one reliable way to level up quickly is by farming XP which means doing an easy repetitive task to quickly level up, one such way is hunting animals for XP, and the best one to my knowledge is Strix I in the Strix System which is close to the right edge of the star map, its a habitable planet that is full of bio-life but most importantly it has a creature called
Flocking Nautiloos Filterers and they are almost harmless and very very easy to kill and some have levels of 80 so they provide really good XP.
location of the Strix System :
https://imgur.com/XvxlTK1to start head to Strix I planet and make sure to land on the biome "Craters", once landed the Flocking Nautiloos Filterers are very easy to find they are a floating balloon type creature and look like a floating jellyfish, they exist in flocks and if you shoot them they will sort of swarm towards you which actually makes them easier to shoot, they can harm you but they move extremely slowly, in about 15-30 mins i easily jumped from level 48 to level 50 and got this achievement, just make sure to sleep with a loved companion to have 15% percent XP boost before leaving your ship
good hunting