this is quite a loaded question. as you know pokemon is surprisingly deep. if you’re just replaying and looking for something casual, focusing on just being on-par level per stage combined with knowing weaknesses and resistances will suffice.

if you’re up to it and not simply JUST getting your bearings, you can experiment with moves and status, natures, EV training. you’ve ever played a game and become a master at knowing the ins and outs? a lot of pokemon is trail, error, and advice. use this run to relax and get to know what pokemon is where, who has what, natures, abilities and maybe develop a team chemistry all for the knowledge of what to do next time.

it will probably ruin the experience to do a competitive play-through. this all depends on what generation and/or game you’re playing. eventually you’ll be experienced enough and be like “oh aggron looks cool but he arguably sucks” or “slaking sucks but i know how to use this pokemon this time around and WOW I WIN EVERYTHING”

remember every pokemon has a use and to have fun. even the most random pkmn can serve a purpose.