It's been a while since I started but I think you want to focus on wracking up cookies so you can get a start on the breakouts, since those consistently give you rewards and you want at least 10 to run.
Matching pets are less priority since you can still mix and match everything outside of trials.
You also definitely want to join a guild, even if someone doesn't make a /vg/ one,because those are daily gems, and the coins you get from it get you strong cookies/costumes. If you're lucky it will already be leveled up and they won't be too picky on people just starting playing.
And if you gather up friends you can send out requests for cookies and people can help you level them up.