I haven't used it since version 0.5.11 at the beginning of December but back then it was feature filled but still a little rough around the edges.  For example there is a paper trader mode where it would apply your strategy to an exchange but not execute the actual trades.  It would then show you your gains and losses had you been trading for real.  But at that time if you restarted or shut down the server, you would lose all of that data. I was running it on my windows mining rig so it wasn't that feasible but I know they were working on fixing that and judging by their changelog this is very actively developed.

I will say though that while this is billed as basic trading bot it does require financial knowledge and the ability to understand charts (all of the indicators, etc).  It comes loaded with a bunch of strategies but you really have to understand statistical terms to really know how to tweak them or even understand what they are.  There is support for pretty much every exchange and trading pair, which is actually overwhelming.  Binance alone has 370 trading pairs, so take that and add 50+ exchanges with the same amount.  You have to know what pairs trade heavily on what exchange, etc.  (at least when I used it) each trading pair had to be selected one at a time, along with a strategy applied to it.  There was no way to mass select pairs and strategies, which i dont know if this would be feasible to begin with.

Support for the bot is good and documentation is decent but it is kind of like reading a manual for a racecar;  It will tell you what all of the parts do and how to put them on, it won't tell you what tires are the best or the best settings for the engine or the best track to race your car at.  They however have a forum for this info:  https://forum.gekko.wizb.it/ 

TL;DR this isn't a magic money making machine but if you invest some time and effort and know what you are doing, it could be