Stock 400 build $2000 to spend?

I bought this project car (91 firebird {originally a 305 TPI)) has a sbc 400 in it, I was told it has a basic rebuild on it, stock everything, i have put on a junior edelbrock intake with a 650 Carb, new lines, alternator, spark plugs/wires, and it doesn't smoke..... Im 19 and have saved about 2 grand, was wondering what would b the easiest and cheapest way to gain a lot of hp. Been thinking about buying top end kits like the edelbrock 435 Hp for $1800... and suggestions or comments will be greatly appreciated. Thank you , btw don't have to much knowledge about engines just the basics