I'd suggest doing cargo missions on the bulletin board until you either ... 1. get 100k or so for a viper. or 2. get 20-30k to upgrade your ship. If 1. then you would eventually end up bounty hunting, 2. I would also recommend bounty hunting in nav beacons with some decent weapons and shields.
I suggest using [
this] to plan out ship designs before actually spending credits. But keep in mind you can sell parts for 100% refund.
By the way, a nav beacon is a place you can target in the navigation tab of the left window, they are usually near the stars you jump to from hyperspace. After targeting the beacon, you can fly over to it in supercruise as if you were going to a station, inside the beacon area there will be random ships flying around. Some ships will be show up as wanted, you can check their bounty on the contacts tab of the left window, after killing the target you can redeem the bounty in a station of the same faction that gave you the bounty. The transactions tab will show you how much you have earned.
Also remember to never fly without insurance! The window to the right shows how much your current ship and it's setup costs, if you have that much money as it shows, you can pay to get your ship back, if not then you start out in the stock sidewinder you get right at the beginning.
Welcome to Elite: Dangerous, commander.