CNHL LiPos are the way go on a budget, you may need to change the connectors on most of them, but this 3s already has the connector. Traxxas connectors are too proprietary and expensive imo. This 2s will need a Traxxas connector soldered onto it.
Steer clear from Traxxas electronics, use a Hitec charger such as this, but you need TRX charge leads here. I made the mistake of buying a Traxxas charger once, it was terrible, slow charge rate and it doesn’t show you cell voltage or IRs.
edit: Hitec chargers also have computer software that...