@Shayuna-Primrose-Azelhart I believe the most common tactic was saving Tokyo Bonus Keys for a couple weeks across multiple characters and then using them all on the first PSO2 Day of Episode 5. Expired keys were exchanged in the swap shop for a new Tokyo Gold Key at a rate of 5:1.
After that I hear Buster Quests are good for EXP on the grind from 80-90 and then there's always good ol' reliable Advanced Quests maxed to +50.
In doing these activities you want to maximize your EXP multiplier and there are tons of ways that stack on one another:
- Concert Buff
- Alliance Tree Buff
- Drink Buff
- EXP item (e.g. 75% up from Ex-cube shop)
- Triboost Item
- Ex Triboost Item (uncommon)
- Daily Triboost (from Daily Client Orders)
- Premium Triboost (in case you've been saving a ticket)
- Party Triboost (not applicable for Gold Keys)
- Weapon with Alternate History affixed (10% to exp) as well as EXP 1, 2, or 3 (can get these on Player shops or while appraising drops from Magatsu Silver and Gold keys ...make sure to choose EXP appraisal as RDR is often a person's default)
- I imagine there are also EXP affixes for units but I don't know for sure (know you can get drop rate ones in the Ex-cube shop)
- Making/Buying/Ordering Timed ability data for your units that increase EXP in whatever area you're grinding (e.g. Tokyo)
I'm sure there are more options, but I'm going off memory and hopefully others will fill in the blanks. Oh, and remember that your subclass will level faster with Summoner as your main class (I think 50%) and you can still use an all-class weapon if you're not a pet person (preferably an all-class weapon corresponding to your subclass to access PAs...though I think a few have built-in PAs).