Im building a budget pc with
16gb of ram
Zotac gtx 1060 mini 3gb
a raidmax delta 1 case
Corsair cx550m
But i dont know what cpu to use a i3 6300 or i5 6400,6500,6600 or should i use amd?
I just want to play subnautica and gtav at ultra settings at 60fps
Okay then the i5 6500 is capable of reaching 70 fps on gta v with ultra settings. Sorry I did not see both are the same price. You should go for the 6600.
If you can afford the i5 I'd suggest either the 6500 or 6600. Usually out of those 3 locked i5's the 6500 tends to be the best value though not sure your location/currency and prices you're considering. The recommendation is based off U.S. pricing. If those are out of your budget then the i3 would be the next best thing for most games. If considering amd I'd wait for zen rather than what's currently available but that may be awhile yet depending how long it takes to get mainstream desktop cpu's to market.
i5 6600 if you can afford the extra premium. I know some people would say to go for the K-version but that is only useful if you are planning to OC. If the 6600 is out of reach then the 6500 would be more than enough to feed the GPU. Also as synphul said the i5 6500 would be the best bang for your buck. The only reason I would take the 6600 over the 6500 is just to future proof you CPU a little more. The performance increase would be about 6-8 fps but that extra power will be useful in 5 years.
I just want to play subnautica and gtav at ultra settings at 60fps
Okay then the i5 6500 is capable of reaching 70 fps on gta v with ultra settings. Sorry I did not see both are the same price. You should go for the 6600.