Im thinking about getting a pickup for my acoustic, just for light use to make it louder for some busking thing, or maybe a small gig, doesn't have to be amazing, so any recomendations?

and i saw this on amazon, and as i got vouchers for my christmas i though i might buy it, anyone used this or is it a bad idea? thanks

Bad idea. I tried it just for fun a while back (one that looks like that in looks and price). Save some more and get a shadow sh2000 (used if u can find one, I sold mine for 30euros a while back). Ain't so expensive and will get u better sound than those
"Steven Seagal is like godzilla for barbies" -> Retard
Try the Artist's Prestige 330. It's a passive pick up and won't break the bank. You can install it yourself or have a tech do it but the installation cost will be about the same cost as the Prestige if you hire it done. I put mine on and I'm no wizard.