Gambits- Dangerous weapon?
Gambits of most types are excellent at almost all levels of chess, but they require a decent understanding to be playable. If you’re giving up material for an initiative or specific plan, you need to understand the plan sufficiently or you’ll just be down a pawn for no reason.
Some gambits are sounder than others. The queen’s gambit is one of the most-played openings in chess; the Evan’s gambit was a personal favourite of world champion Garry Kasparov; the King’s Gambit was an incredible tool for romantic chess players. But there are tonnes of gambits that are unsound, or even fully refuted by correct play.
Either way, I’m not sure they’re super important to someone who solely plays bullet (and at the sub 1000 level), as your games will rarely be decided by the opening choice.