tips for getting starters in a living dex

hey everyone. so i’ve been recently working on making a national living dex for black 2. i just finished the regional living dex today, and im just kinda feeling overwhelmed with next steps because i know i have to play multiple games…making me question if its worth it and if i should just try and do it in gen 7 instead. but anyway one of the issues that seems to be the greatest is trying to get the starter pokemon. since im doing this in gen 5 its hard to really trade because while there is the service there’s not too much on it, especially starters. i do have a second 3ds and for a few games a second copy, but how long into a game does it take to unlocking trading?

i guess to keep it short in just wondering if people know any kind of tricks or helpful info to get multiple different starters. thanks!