Couple tips I've figured out:
You can farm SSR summons and weapons without TOO much time investment (especially given how easy to get AP reset pots are). On the quest map, the bright red rectangle that takes you to BP fights, click on the grey rectangle to the left of it. One of the selectable options will have Hard/V.Hard/Extreme/Maniac and a gem reward offering (picture will look like one of the available summons you may have seen). Hard is doable pretty early, V. Hard is doable around R35ish or maybe earlier if you have a strong full element party. The drops can be redeemed in the item shop under the tab that kinda looks like a FFXI garuda. Dark Fencer for DEF/ATK down and slow is king here, and characters can debuff help a lot. 20 runs of V. Hard will get you a SSR summon, 15 runs for SSR weapon.
I saw at least 1-2 people pulled a Metera, here's some advice: Build a fire squad and go to town on wind stuff to build up your wind team (BP fights / farming / etc). Dark Fencer DEF- with Ability Damage+ II set as extra skill lets Metera do around 120-150k in one turn with her abilities (in comparison my slow ability on DF does 20k with same buffs). It is incredibly silly. There's a fire SR girl in a plaid skirt who gives fire damage+ to full party, she's really useful too if you have her. The default story fire guy is at least usable.
Use your BP. Even if you don't have time to really play, just enter a Magna (2 BP required) and summon as soon as you enter and then just go AFK. You'll still most likely get 4 gold chests which will give you SR/SSR items, items needed to buy/upgrade stuff, and weapons that give 500-1000 exp per use for upgrading weapons. (I just got Leviathan SSR dagger from hosting Magna despite contributing almost nothing to the fight).