If you wanted the long way, just play every season, and collect the V-Bucks. After you collected 1000 V-Bucks, you then buy the Battle Pass, which grants you lots of stuffs, including skins, emotes, and another V-Bucks.
The short way? Find several free skins out there. I know Playstation Plus and Twitch Prime members can claim free skins, and there could be others. But always remember that there's loads of fraud websites that offers free skins/V-Bucks, so be careful.