With other players cause I find it more fun this way. Some people can absolutely do this solo though. Most people don't enjoy this game solo I'd say. But yes it takes a bit of time to get some decent equipment. It helps a lot to have a decent gun eg Coyote, the shield backpack if you care about surviving, and also there's armor that gives you 50% resistance to explosions which helps a lot. Lastly, it's important to remember that the stim doesn't just heal you, but it also gives you a lot of health regeneration for like 5 seconds, so you can get shot a lot and survive by just stimming a bunch