In Riders of Icarus, honestly I don't think there are any real guides yet, however there are some tips that you can get from this sub-reddit and general information searching on the net and some interesting videos on YouTube. I know as a priest, at least at the initial levels, I've felt very powerful compared to while I had my assassin at the same lower levels (don't depend on this later on though). Here are a few tips I've learned since starting to play - I know there are many people out there much more advanced in the game than I, but hopefully these will show you a little help.
should make sure do all of the quests – including main and side quests, you may
even choose to do some repeatable quests now and again. Last thing really you
want to do is fall behind in level if you can avoid it.
Even being a 1 or 2 level deficit can be a major pain with the amount you'll
potentially miss, I'm not saying you can't deal with mobs and quests that are a
level or two ahead of you, it's just easier to keep at level.
More information you can check:https://www.mmogah.com/news/title/riders-of-icarus-tips-from-a-senior-player