Right now, your best choice *IF* you have enough money for 3-4 of them would be the S9 - but IMO wait for the price to come down some.
They'll do the best job of "loading up" your amount of free power the most efficiently - and nobody has announced anything that can top their efficiency by a noticeable degree, much less has anything competative in production RIGHT NOW as a miner.
Thanks for advise. I actually already thought about waiting for the price to come down. I think before I'll gather sufficient information about the rigs the price will come down

Honestly I would start off small to. If your budget is 5k I would not go all out right away. Get less gear and make sure you have enough money for cooling, shelving, PDU, etc (depends on your setup).
But if you start out small it's easier to add more and you can do it hopefuly easily and you will know your setup's limits. One of the worst thing for miners is buying them and not having all parts ready, so you have downtime.