Why do you feel limited on bittrex? Bittrex is imo probably one of the leading altcoin exchanges right now, if not the #1 altcoin exchange(since poloniex has so many issues with deposit and withdrawal, plus their almost non-existent support).

I would definitely go with bittrex, if i were you. They have substantially more markets than poloniex does and a lot more liquidity than yobit, cryptopia, etc.

If your day trading involves fiat, then go with Bitmex/bitfinex because you are able to leverage your trades as well as trade with fiat. Just make sure that you have your identity documents ready, even if exchanges say that you can have an anonymous account doesn't mean they will keep their terms and conditions like that.