I think the term you are looking for is a mining "rig" (or mining computer). A mining pool is what you typically connect your mining rig to in order to submit shares and get a % of the block reward based on how many other miners are using the same mining pool.
Depending on where you live and the prices in your area it may be possible to build a mining rig with 6 Rx 580s for $3000.00 - here in the USA I believe you could manage it for as little as $2500 with a bit of luck and allot of shopping around. $3000 would definitely be enough based on prices here, but it may not be enough in many countries that have higher prices on computer parts in general.
Ok, thank you I fix the tittle Depending on where you live and the prices in your area it may be possible to build a mining rig with 6 Rx 580s for $3000.00 - here in the USA I believe you could manage it for as little as $2500 with a bit of luck and allot of shopping around. $3000 would definitely be enough based on prices here, but it may not be enough in many countries that have higher prices on computer parts in general.