Getting girls jealous

I [20M] am currently in the friend zone with Sarah [20F] but I really like her. However, I'm not super attached to her and have been meeting other girls like Ashley [20F]. Ashley is pretty hot and I definitely want to get with her, but Sarah is still my first choice. I'm 90-95% sure Ashley likes me. Also, Sarah and Ashley don't know about each other at all and I don't think Sarah has ever seen me with any other girls before (partly the reason why I'm in the friend zone). Honestly, I was a late bloomer socially speaking and I've known Sarah from the time when I still the socially awkward kid. I'm trying to change her perception of me from a socially awkward nerdy guy to an outgoing chill sexual person.

Anyways, tonight there is college party happening hosted by members of our university's salsa club. Both me and Sarah are members and we are allowed to bring one guest if we want, and I chose Ashley for a couple of reasons

1) To make Sarah jealous as a way to escape the friend zone. I don't want to just ask her out because she currently has very little, if any, attraction towards me and I want to build that first before making any big moves (otherwise I feel like I'm doomed to failure). Sarah hasn't seen the sexual side of me (she probably thinks of me as her gay guy friend) so I was hoping to demonstrate that new side of me to her as I hang out with Ashley and make moves on her.

2) Even if my attempt to make Sarah jealous fails, I can use this party as a way to escalate with Ashley.

My question is, as I'm hanging out with these 2 girls tonight, what are some tips/advice to maximize jealously and competitiveness between them? Assuming jealously works, how do I make sure I don't take things too far and make one girl feel alone or second-choice thus ruining any attraction I might have built up?

Also, I want to invite both girls over to my place before the party to pregame. Is that a good idea? I was thinking that if these 2 girls initially meet at a more private setting (my place vs crowded party), the chances that they'll get jealous faster will increase. Additionally, a little bit of extra alcohol would probably be helpful in this case. Both girls will be more receptive to my moves, I'll be even more confident, and if something goes wrong like Sarah rejects me, I can just blame it on me being drunk thus saving saving our friendship from getting awkward

.

UPDATE: Sarah just texted me saying that she's not going out tonight because she has 2 exams next week. Should I ask her once more to come along with me by saying that she should take a break from studying all day or just leave her be?