The sun is bad for your skin if you get too much of it. There are self-tanners now that are very realistic and not orangey like the old stuff. That’s the safest option. Look for one that says ‘noncomedogenic’ though since you have acne, it won’t clog pores and lead to further acne.
I found that a little bit of sun actually helped my acne. I never laid out until I was drenched in sweat, though. If you want some sun, do it naturally, like laying outside for a while, this also boosts your Vitamin D production. Don’t get in a tanning bed, it’s hot, and sweaty, and you’re laying agaisnt plastic…who knows how well they really clean those things anyway! Remeber always do things in moderation.