21st birthday party drinkers

I am throwing a suprise 21st birthday party for my gf in a couple weeks.

I’ve never thrown a party – there’s like 20 ish people coming – most of which will drink 2/3 cups I’d assume

Any ideas for what drink mixes to make in a big jug while keeping it tasty but AFFORDABLE.

My original idea was too expensive so any help would be appreciated thank you!