My advice: Don't listen to people (*cough* youtubers *cough*) that try to tell you which star card loadouts, heroes, classes or weapons are "the best" because what really is the best for you, well, has to be determined by yourself. What fits great to the play style of someone else doesn't necessarily fit your needs as well and vice versa.
There's nothing wrong to take a look first at how the star cards or some features work exactly (and which ones don't work as intended or rather work against you) but the decision about your loadout, class preference... really shouldn't be made by someone else.
The wiki stats page on the other hand really can be a great help (especially for hero characters), as this page helps to clarify dmg and other stats that are not properly or not at all explained in-game.
Another advice: As a newer player, play Co-op to easily unlock most stuff, especially when you want to grind certain clases that you normally don't play.
However, don't think that what works greatly or poorly against bots works against human players the same way. Yeah, I'm referring to the common tip to play Co-op to train your skills and determine which weapons etc. you want to use in multiplayer. This only works to a degree and won't give one a right insight about how this stuff will come out in multiplayer.
TL;DR: Play Co-op only to unlock and test stuff, play MP to actually train your skills and to find out which of the unlocked stuff/abilities you really want to favor.
