All of the below is assuming you do not wish to invest real money into the game (which most of us don't recommend until you know for sure what you're doing and whether you want to stick with it).
If you are that low in level, my suggestion would be to work through the prologue episodes. You'll get some much needed covers, ISO and HP. As events come up, join them with the expectation that you'll come in last place, and be pleasantly surprised if you do better. Even last place rewards will be of benefit to you. And sometime soon, you'll stop placing last and earning real rewards. Note also that if you can load up the nodes as soon as an event starts, you will get super easy seed teams that you should be able to beat on even at your level.
Focus on a decent character or two over spreading out the levels. Iron Man is a good candidate at the star level you are at. 1* Hawkeye and 1* Black Widow, not so much (but hey, if you like them, it's your game!). If you were able to grab the free Hulk in the event that just finished, it will be tempting to build around him, and that's not a bad idea, if for no other reason than his ability to tank. However, don't expect to get the second cover soon.
You are quickly going to be in a situation where you need to either invest in roster slots or decide who to drop from the team. So plan accordingly. Keep in mind that the money you receive from selling characters back is based on level, not number of covers. So a level 1 Hawkeye with 5 power covers sells for 80% less than if you sold each cover individually.
Lastly, join an alliance, even just some random one. You might be kicked out, but try another one and another one until you stick. Just being in an alliance increases your rewards. I don't know how active CAGsual Slacks is these days, but maybe Kerig can find a spot for you. Broly can get pretty cranky if you aren't pulling your weight in CAGvengers (

), but if you are enjoying the game and start seeing some positive results from your efforts, we can always kick a random to see how well you fit in.
Other than all that, the OP has some links on getting started in the game. I don't know if they have been kept up to date, but they're probably still valuable resources.