Team RCC went LiPo early, and the less expensive ones too boot. (I myself prefer the HK Zippies.)
Even if they are "hobby amp rated", they do a good job in all our machines now.

Charger. Imax B6 is the basic charger. You can't go wrong with that one, as long you don't want to recharge large packs in 10 minutes.
I believe most affordable 50W rated chargers just use the same basic technology, maybe repackaged with a 4 in 1 box, or with an extra LED to tell somebody something.