1. There are many ways to gain Steempower. The best way to do it without spending your own hard earned cash money is by creating a successful blog. Creating a successful blog is a whole post in and of itself. I have two posts here that can help answer that question. One is about making better quality posts by @ethandsmith linked HERE! and the other is about leaving quality, engaging comments by @ogochukwu and it is linked HERE!
2. You use roughly 2% Voting power with a 100% upvote, and you recover about 20% voting power in a 24 hour period. So you can give out roughly 10 full power upvotes every day. You can see what your current voting power is (and a few other cool things like what your current vote is worth) by going to https://steemnow.com/ and inputting your username in the upper right hand corner.

I hope these answers help