I'm a lightweight too or at least I was when I first start drinking, but lately I've come to find out I actually built up a bit of a tolerance. Anyways I would suggest if you want to mix a drink that cherry mcguilicuties (spelling?) and 7 up is pretty good or vanilla mcguilcuties and coke is good too and tastes just like vanilla coke. Those are too of my favs and they don't get you too drunk right away if you drink in moderation. Otherwise pineapple and malibu is pretty good too but the alcohol is a little bit more in the malibu than in the cherry and vanilla stuff. Anyways hope this helps! :)
I think the best drink for you is anything without alcohol. If your allergic, then don't do it. Your health is worth more than that. Drinking is over rated anyways. You can have fun without it, I always get a laugh out of watching my friends act like idiots when they drink. It makes me thankful that I'm straight edge.
Jagerbombs don't have too much alcohol, but they can be pricey sometimes. Sex on the beach is one of the first drinks most girls have. And you mentioned not liking beer, but there's this Irish beer that doesn't even taste like beer. I forget the name, I'll try to let you know. but I know it wasn't Caffrey's or Guinness.
IF you like mikes hard lemonade, than I assume that you like vodka. SO what you could do is have a drink like a vodka and cran, but instead of having it in a small glass, have it in a large glass, still only use one shot, but add more juice.