Well, upvoting and resteeming doesn't cost you any steem power or SBD. Upvotes use your voting power, which gets down with each of your upvote and is filled again automatically by around 20% every 24 hours. You can check out your voting power on steemd.com. Also check out steemstats.com and steemdollar.com.

Resteeming doesn't cost you nothing. It's just way of sharing a post you liked with your followers. People usually resteem a post which they have upvoted, so that it gets upvoted more after them which in turn earns them more curation rewards. Hope it helps.