I'm starting to resent my friends that don't work.
Why do you resent them for not working?
I work so hard every day and they get to be lazy.
It may seem unfair that you have to work hard and they don't. Don't resent your friends though, it's not fair to them and will hurt your relationship.
It is fine. I'm going to buy them sweaters for Christmas.
That is very generous. It is good to buy gifts for your friends. It is thoughtful.