Let's say you already have a pair of clowns and a basic 10g...
Few ceramic tiles for egg attachment
Extra 5g, 10g, 20g tanks
Couple extra air pumps, lines
Sponge filter
LIVE rotifer culture
Live phyto cultures or a solid supply of concentrated phyto paste Nannochloropsis, Tetraselmis AND Tahitian Isochrysis to round out all the nutritional needs of the fry
Artemia eggs
Separate fluorescent bulb setup
After you get all this and have spent less than $200, you're doing good. You can get most dry goods cheap but its the live cultures and the time invested to build up a reasonable supply that is costly. I would say you need to get your cultures running 2-3 months before you even think about breeding clowns.
Its been a while since I had to buy starter cultures and I broke down my setup a while ago. Not much free time within the last year's time...