I can prolly only afford a manual one will that mess up my car if i boosted it to much?? What kind should I get and are they easy to use?

Mainly what kind should i get

 

theres all sorts and they work all the same.....if you dont want to spend alot...get one of the ones off ebay that you can put inside your car....i use that one and it works fine...it is better than the average manual boost controller in that you dont have to get out and pop the hood everytime you want to raise or lower the boost...