What exchange do you use?

[coiner2018]

"Ideally I'd like an exchange that I can put strategy graphs onto back data, GDax lacks a lot in this area."

Re. this point - I don't think I'd choose an Exchange based on its charting... I think charting and analysis are most likely best kept separate from the individual exchange you're using.  (Unless I'm misunderstanding what you mean here...)

Eg. GDAX is good because of no maker fees - but obviously their charting is rubbish.  From an exchange point of view - the fees are way more important than their charting, in my (albeit limited) experience.

I've used the excellent TradingView with the GDAX pairs to apply various strategies for analysis (some users have replicated Gekko strats as Trading View strategies).    Have you imported historical GDAX data into Gekko for backtesting?  1-2 years worth of history is worth importing for this purpose, and doesn't take too long.