Best prevention is injecting more often. Fluctuating levels of hormones in your blood are a BIG factor for acne (hence why so many get it around puberty/high school/college-age). Even with something like test-e, if acne is a big concern I would honestly take lower doses every 2 days (150-200mg EOD of test-e if you want 500-600mg/wk).
Besides that, isotretinoin (aka accutane) is the absolute best medication ever developed for acne treatment/prevention. There's really no way of getting around it. Usually I wouldn't recommend it for simple acne, but you're asking for "the best" product: well there it is. Thing long and hard before taking it, but it is medically without a doubt the most effective and proven acne medication ever invented.