Looking for something that will hold up in the heat, provide medium-to-full coverage, and not aggravate my sometimes oily, acne-prone skin. (reasons why you like it, as well as its drawbacks, would be helpful too!)
Thank you!
(concealer recommendations welcome too. )

I have used the Cover Girl liquid foundation products available nationally for about $3.50-$5 for many years. When I want to splurge to get a free gift, I go to the Lancome counter and buy the very lightest foundation they have. Neither of these is comedic (causes outbreaks) and doesn't look like war paint. If you have acne-prone skin, full coverage will make your skin look much worse.

Tinted moisturizers are a nicer and lighter alternative to concealer or foundation. They're great in the summer because they're so sheer.

Whereas the two latter can get cakey when applied atop of dry skin, tinted moisturizers even out skin tone without risk of looking overly made-up.

Sadly, they are quite expensive. But you can rectify this problem by making your own: just mix one part day-cream/moisturizer, one part liquid foundation, and one part sunblock (optional, but certainly a good idea!) for a relatively affordable replacement.

If you're intent on buying the real thing however, I've found Marcelle Sheer Tint Fluid Moisturizer (available at most Shoppers Drug Marts) to be the easiest to blend in, even above the Burt's Bees equivalent.

Anyway, if you're looking for a summery, low-maintenance look without risk of visible complexion flaws, this is the perfect thing.

Hope it works for you!

Try MAC studio fix foundation, i use it and it seems to stay on.

For Summer, I would choose any foundation that has any sunscreen in it, so it will protect your face from the sun and will probably wear longer. I have recently been using Maybelline: Wonder Finish LIQUID to powder, but i know you asked to not recommend any powders. But i will say one of my friends hates using foundation/ any powder on her face because it looks unnatural and she doesn't like the way it feels, so when my mom was putting on her makeup i recommended this stuff to her and she tried it, she said that if she was to ever wear powder anywhere else it would have to be this stuff.
GOOD LUCK! and GOD BLESS!!