hey guys I have for some time wound my own air core inductors using this online app.

Pronine Electronics Design - Multilayer Air Core Inductor Calculator

its quite accurate and useful unless you want to use wire finer than 45AWG

for BIG current I like 18AWG and was happy to find this wire on Ebay

18 AWG Gauge Enameled Copper Magnet Wire 200C 5lb 995ft Magnetic Coil Winding | eBay
$57.26 shipped
5lbs
995ft
<$0.06 / ft They have 45 units to sell and its pretty cheap