Warning: be careful. We've tested over 150 commercial EA's, and over over 100 free EA's. Most are scams/crap, or only work on demo accounts. Less than 10 of all those EA's actually passed our most rigorous testing.
Then firstly: I recommend you learn about Tick Testing: https://www.eareview.net/tick-data
With that you can visually test an EA on a realistic spread (double your broker's spread to take slippage and execution speed into account).
Secondly, if you do buy one, run it on demo for a while, and try buying those through clickbank or other reputable payment gateways that will give you your money back if it is a scam.
Third: try to avoid martingale EA's, there might be a few that haven't crashed yet, but 99% of them crash at some point. Also be careful with grid trading EA's, most EA's that call themselves grid EA's are actually martingale.
Four: really, the best thing to do is formalize your manual trading rules. Figure out how and when you trade, and why. Write it down, and program an EA to follow those rules to the letter, then test it on tick data (We've done this with at least 50 strategies). If you don't want to learn MQL, google Steve Hopwood, he programs EA's for free publicly, or privately for 100$, and he's good at it.
Hope that helps!
When you fall you learn, then you get up and you try again until you master it.