SMC LiPos are pretty good: https://www.smc-racing.com/index.php?route=product/product&product_id=641
There are a bunch of other cheap LiPos on Amazon that seem to have good reviews (it's also prime day, so some are discounted)...
Castle Creations Copperhead 3200kv. It is sensored capable and takes up to 4s, and from what I've heard, they run pretty cool (the Copperhead ESC also has a pretty strong BEC). I have Castle's 3800kv motor, and I have to say Castle motors are as smooth as butter and have great low-speed startups...