i found the kawakami max rank perk to be extremely useful. it essentially increases your free time by 100% on certain days. takemi's higher rank perks allow you stay in dungeons longer for the right price

here's a non-spoilery tip: towards the end of maxing confidant ranks you tend to get a lot of bonus social stats so don't spend too much time on activities like studying and taking baths. i put a lot of effort to getting my social stats up and ended up maxing everything except guts before entering the final (?) dungeon (the casino) so now i'm stuck with hanging out with people i don't want to or fishing, which i perceive to be a waste of time

also get that strength confidant rank up ASAP and grind yen in mementos when you don't have anything else to do. i have a persona that is at least 20 levels above the protagonist's level because i did both of the above