informal or formal?

Depends on what chapter you're rushing. Normally the "stronger" sororities doing informal can be more selective and usually end up going with girls who have lots of friends in the most recent pledge class or 2. Also keep in mind they sometimes only have only 5-10 spots to fill and 50+ interested so you're not guaranteed anything just because you rushed informally like you are in formal if you stick out the process.

Also, did you get dropped from formal or pull yourself out? If you were dropped I would tell you to wait until spring semester again. If you dropped out of recruitment I would consider doing informal, but definitely avoid saying things like "I only had chapters I hated left" when you go through informal

I wasn't eligible my freshman year in the spring. Then did informal in the fall, then formal, then informal again before finding my home.

Formal Again
•Odds are you won't meet the same girls if you do formal again. However, before doing formal again think about why you honestly may have been cut (if you were cut from all houses). (i.e. If your GPA was below a 3.0, it may be worth trying again because a lot of houses probably cut you for your GPA).

Informal
If you're not good at small talk, informal is NOT your friend (you need to be able to pick up conversations quick). You have to be very proactive with informal. If a chapter is holding multiple events, try to go to ALL and talk to A LOT of girls. If you know a girl in a chapter doing informal, ask for a recommendation letter. Informal is super selective (minus chapters way below quota, but I only see AOII not being very selective), so don't be discouraged if you don't get a bid. It's a LOT harder, but a lot more laid back.

Side note:
Consider non-PHA sororities (if you're an agriculture major Alpha Sigma Upsilon, or an engineering major Phi Sigma Rho ; They're both social and like normal sororities, just with a major requirement and smaller.). Do research and look into all chapters, not just the ones you see during formal. Keep an open mind & heart. If a chapter offers you a bid, don't be picky and deny it. They saw something in you that you haven't seen in them yet. Your eyes will open as you learn more about them.