...Make a Living Dex!
This guide is based off of the techniques I have personally used over the past nine years. I play hard copy games, so therefore I have no idea how playing emulators or something else will affect progress. In addition, this guide is referring to Main Line games only. I also do not use cheats, and I personally like to keep the OT to be myself as much as possible.
In addition, my points here are slightly vague as every game will have additional mechanics to boost things such as egg hatching, friendship, etc. Please take time to do further research on particular games - thought I have made a follow up tip list for Gen V!
My Gen V Living Dex tips
Coming soon!
My Gen IV Living Dex tips
Why complete a Living Dex?
Similar to completing the National dex, completing a Living Dex gives you the oppourtunity to explore the depths of the chosen region, and use Pokemon, Items, and features you might've never used before. It gives you the opportunity to flex some organisational skills too, and it is so very rewarding and exciting to watch it all come together! And should you ever need a particular Pokemon, you've always got one at hand. It has helped me to get so much more out of Pokemon games, and I get a lot of long-term fun and fulfilment out of it.
Choosing a Dex
In each mainline game, you can make a Regional Dex, or a National Dex, if you've reached the post-game. In newer generations, the National Dex looks very different. It is advisable to check out this page to see what Dexes you can make with your chosen game.
List of Regional Dexes
List of every Pokemon by National Dex number
I recommend starting with a Regional Dex, as they are generally a lot smaller and you can obtain almost every Pokemon apart from version exclusives easily. This is a good option if you've just started a new save file, but it can also be done in the post-game.
Pokemon XY/ORAS are the last Main Line games to have a full National Dex (721 Pokemon total) in-game. In Pokemon SM/USUM, there is no National Dex, but you may use any Pokemon (807 total) in-game - so you could in theory make a National Dex in these games. In Pokemon SS/SV, you cannot use any Pokemon in-game so it is not possible to make a National Living Dex (898 total as of SS, 1010 total as of SV) in-game. Instead, National Living Dexes can be made in Pokemon Bank or Pokemon Home.
Like the National Dex, choosing to collect all various formes and gender differences in a Pokemon, as well as collecting mythical Pokemon, is optional. Some people even work on Living Dexes made up of completely Shiny Pokemon!
Preparation
The beginning stages will look quite different depending on if you're starting with a new save file or not. I recommend to reorganise your PC boxes as soon as possible!
I keep the first few boxes empty for Pokemon to be sent to as I aquire them. The Living Dex boxes will be named according to dex number - 001 - 030, 031 - 060, and so on. I also keep boxes for Pokemon I want to trade, eggs to hatch, and duplicates and uncategorised Pokemon. You can approach this part of the organisation however you like.
I then work through all the Pokemon I have and place them according to their dex number, using a guide. Here is a visual example of one of mine. Doing this gives you a good feel for what you already have, and is motivating to add to over time and watch the boxes fill up!
There is a level of organisation required outside of the game. I personally use good old pen and paper to keep track of the Pokemon I am missing, but I've known others to do this in spreadsheets, or even online tools like this one. Though I have official game guides that I use, and of course the in-game Pokedex, I also rely on sites like serebii for more specific information, like rate of appearence or time of day.
Filling in the Gaps
From here, there is really no linear way to approach this. You could go number by number, box by box, area by area...or focus on breeding first, or batch evolving Pokemon. I usually go box by box as it'll encompass a wide range of methods and it is very motivating to fill up that first box!
Below are the common methods you'll have to encounter, and ways to make them easier.
New Save Files
If you're starting from a new save file, be sure to catch one-two of every Pokemon you come across - this way, you make progress in the game and the living dex at the same time. It may be useful to use guides to catch multiple of version exclusive Pokemon for trades, or for Pokemon you'll need to evolve as they can't be obtained elsewhere. I'd also make sure to scour every area and battle every single trainer, so even if you dont catch everything, youll have the 'seen' portion of the dex filled out to help for referencing what you do or dont have down the line.
EXP Harvesting for evolutions
Alongside breeding, levelling up Pokemon to evolve them will be one of the most time-consuming parts.
To quickly level up weaker and newly hatched Pokemon with low evolution levels, have them in your party/holding an EXP share and battle strong trainers or Pokemon.
For Pokemon that have higher evolution levels, such as levels between 35-50, keep them in the first slot of your party and switch them out if they are too low level to handle the battle. This counts as battle participation, and any participation in a battle will gather more EXP.
Have the Pokemon hold a Lucky Egg if they are participating in battle for more EXP.
Change the OT used to grind these Pokemon. If you trade to another version in the same generation, the OT will be different, meaning the Pokemon will get more EXP. For example, in Pokemon Pearl, trade the Pokemon over to Diamond/Platinum/HGSS and grind their levels there.
To harvest as much EXP as possible rematch strong trainers. This method varies by game. please reference this link to see where you can find rematches in the relevant game. This includes making use of vs seeker, pokegear, or pokenav, and also rematching your rival. If you feel, you could rematch the league.
Breeding and Hatching Eggs
The easiest way to breed Pokemon is with a Ditto, and you should get one as soon as possible. Here is a list of Ditto's location in every main-line game.
As this is my least favourite stage, I try to batch all the breeding and egg hatching I need to do together, so that while I wait for an egg to appear at the day care, I can run around and get steps on any eggs in my party, and hatch some. To make this more fun, as you collect eggs, randomly store them in a box and shuffle them around to make the hatching a surprise XD
Have a pokemon with the ability flame body in your party to speed up hatching.
Trades
Be sure to check what trades you can make with in-game NPCs.
Check what Pokemon are version exclusive, and ensure you catch numerous of each. For example, in Pokemon Diamond, I would catch three Murkrow - one to keep, one to evolve, and one to trade for Misdreavus. I'd also do this with my starter Pokemon. For example, if I had chosen Turtwig, I would breed it for 4 eggs - two to trade for Piplup and Chimchar, and two to evolve to Grotle and Torterra.
Try to catch multiple difficult Pokemon you could use for trades later on. This is more of a time-sensitive trick, but in Pokemon Moon I was able to get another type:null by breeding many Mareanies to evolve to Toxapex, as this Pokemon seemed to be highly sought after.
Use the GTS if avaliable to trade Pokemon. I usually rely on just this and people I know, and I've met some very generous people who gave me missing legendaries out of the kindness of their heart! I'm sure there are lots of communities out there that could be willing to help!
In Gen IV and V, it is possible to get onto the GTS. This is crucial for some dexes such as the New Unova Dex, where some Pokemon are impossible to obtain, or even see, without trading.
pkmnclassic - Unofficial server to get online in Gen IV and V. Allows you to see what's avaliable on the GTS.
Going Online in Gen IV and V - Guide on how to get online in Gen IV and V, with a list of servers.
Transferring from Previous Games
On the 27th of March 2023, the 3DS store as shut down, meaning invaluable tools like Pokemon Transfer and Pokemon Bank can no longer be downloaded - though if you already have it, the use of it will be free. If you do not have it downloaded at all, you won't be able to move Pokemon from BW2 or previous over to the 3DS, and you won't be able to move any Pokemon over to Pokemon HOME.
Depending on what games you already own, you may be able to make significantly more progress by transferring Pokemon from other games over. This is how I was able to complete the living dex in Pokemon Y. I went back game by game, gathering pokemon I couldn't obtain in Pokemon XY/ORAS, and moved them over. WARNING: Please be careful with what Pokemon you decide to move out of the game, as they cannot return. I made the mistake of taking all my beloved pokemon teams, favourites, and legendaries through to the 3DS - which while its wonderful that I still have them, it means my save files are very empty and I feel less of an incentive to play them. This is a good idea if you intend to restart the save files anyway, but a not so good idea if you have trouble letting go of old save files like me...I'd rather get another copy of Pokemon Pearl than restart my very first game!! Sigh...