I've gotten great results using the Macegrow 450w LED. It's a combination of COB and LED. You can find it on Amazon for less than $70. Reviews are spotty so maybe they have quality control issues. I've got 2 of them and they both work great. I've been using one for a year and the other one for 4...
Gnatrol WDG works great for me. Use it in every watering for about 2 weeks and the gnats will be gone. It's totally natural, it's a bacteria that attacks the gnat eggs. You can buy it on ebay or Amazon.