To say this is a loaded question is an understatement, but I will chime in.
The quickest way to increase power in a big way is a supercharger. Not cheap but its bolt on and lots of good kits out there with great tech support and lots of threads on here from folks who have done it. But is costs $$. In addition if you dont beef up the transmission and rear end you may have issues there. Cold air intake kits, headers and programmers are the only cheap/easy install things you can do but they really dont move the HP
needle on a 5.3 that much. In my case I added a cam, headers, different heads and injectors along with a custom tune, and also had my 4L60E rebuilt and beefed up. Truck was a good bit faster but my 5.7 Hemi Ram with the 8 speed transmission would still eat it alive. If you have a 6 speed that might be different. A 5.3 can make massive power if you want to spend enough, Hot Rod magazine took a junkyard 4.8 and made 1600 Hp with a twin turbo set up on a bone stock bottom end, and could not blow the engine on a dyno even when they tried. So they will make big power.
But unless you are willing to spend supercharger type money, you will only see modest gains from the inexpensive easy bolt on stuff.
