Quick JP starter guide

Starting
After title screen there is the terms of agreement for the game, click the middle one (2nd option) to progress
Do the tutorial
If you are rerolling, which I highly suggest, you want to go directly to the summon menu and do your roll right now
You will always have enough for a 10 roll, and an ace ticket and a 5* ticket; maybe more if there's an event going on

Rerolling
Non Root: Delete cache and relaunch
Root: Go to your file explorer go to apps shared_prefs and delete the Aska.xml file

Beginning
Push through the story as fast as you can while doing the starter missions, if possible save your MoT until you get that starter mission; JP reset is 2am JST, or 12pm pst/3pm est
You will be able to sustain pushing really far with level ups and stamina tickets the story gives you, you want to use 50/200 stamina tickets first over the full restore ones since there is stamina overflow

When you reach 40/60 maximum stamina (not overflowed) you can start first clearing some event nodes so you can join events when you will eventually run out of stamina to do the story
What you want to do is spend all your stamina on story while joining multiplayer to progress

Event progression
Priority for events are the seasonal/collab reruns and the newest events, since those would be the most populated and easier to get into rooms
The caveat to this is that it will be a long time for the rerun if it even does (collabs mostly)
Note: you can check boss weakness/resistance on the join/create room screen, its the button on the top right

What to buy from shops
If you don't want to buy packages which accelerate your first character, you want to prioritize limit breakers

tl;dr
LBs
Barrier Blaster
AP seeds (for long term)
tickets
everything else (welch's love fluids and the cake thing are good things to grab first)

note: they give you a shitload of weapon tickets as you play more so don't prioritize event weapons unless you have literally nothing for your character