My best tip would be to get a couple of good relays. I'm gonna zap you the fee for mine (https://nostr.thesamecat.io). I would also look at filter.nostr.wine because it aggregates a bunch of other public relays, which you can then remove from your relay list.

I only have 10 relays, and I'd say it doubled my battery life on Nostr. Still tough, but not near as bad.