Reaching level 50 will not take very long, roughly 12-15hrs if you’re mostly playing the story missions with some side activities. XP is awarded by virtually anything you do in the game. Playing story mission will level you up the fastest, but playing PvP events, faction missions, skill games, visiting landmarks, hacking data stations and discovering wrecked parts will all go towards levelling up. A perk is also available to you by Zoe called Missionary which will ultimately give you a 10% bonus to all story mission earnings in the form of bucks and XP.