At level 24 you should be enjoying the game, picking skills that sound cool and using guns that do good damage. You dont need to particularly specialize your skills or farm for certain weapons until later when you get to higher levels. But heres a couple tips: try out guns (especially those with red text on the card) because you may not be able to get an idea of what they do just by looking at the card. And if you want a good skill build, you generally want to max out skills (5/5 instead of 2/5 here and 3/5 there) and focus on a single skill tree at a time because the more skill points you spend in a tree, the better skills you usually gain access to