What to transfer as a new player?

I just started playing Pokemon Go a few weeks ago and I am constantly running out of space (725 total). All of the transfer advice I have found seems outdated. I mainly do PVE with the occasional Great League PVP match or two when I'm bored lol. I know to keep hundos, legendaries, mythicals, shinies, costumes, etc., but is there a good transfer string to help me out before I get burnt out constantly cleaning out my Pokemon? I'm not interested in a living dex. Thanks!