OP. You don't need to spend a ton of money to get flawless coverage. You need to learn how to use the products you have.
First, you need a good primer. I HIGHLY suggest monistat anti chafing gel. It's what I use, it's what I use on my clients, it's what I use on my models. I love it. It gives you flawless coverage and it's under $10 as opposed to spending 30+ for primer that sucks.
Second, you need to know what colors to use. What color is your acne?
Use this color wheel to figure out how to cover it up. Find the color that you want to cover and whatever the opposite color is, is the color you need to use to cover it up. So, let's say your acne is red. You'd need a green tinted concealer. Easy right?
Third, you need a good full coverage foundation. Everyone is quick to suggest MAC, but honestly, all you're paying for is the brand. MAC's not all that fantastic. I have it, but eh. I love this stuff:
It has great coverage, it goes on smooth and lasts forever.