Recently started seriously playing 
and struggle to keep up in cs. I'm pretty good at last hitting with autos but then get shoved into tower if I don't use spells that I'd rather use to harass. Is it better to use abilities to cs more early or be aggressive?
Despite what you may hear even LB's skill floor is relatively high, with farming being a major issue. I really don't recommend LB, making use of her is extremely difficult and she's not strong right now. It's one of those champs they've left intentionally pretty (overall) weak due to backlash.
In this season you really can't be aggressive early, mana regen has been nerfed into oblivion in S5 so unless you're stacking 3 Doran's there's no way to be nearly as aggressive as before early game.
Leblanc kills minions and farms champjons
Max W if you're really getting shoved THAT hard
W
It is important to pick when you want to trade. Spamming abilities is something you never want to do, unless maybe youre going to back right away and you know it. Wait for your opponent to have at least one cooldown on a major ability and then try to trade, and you will make the most of your mana usage and come out a lot further ahead on the trade. Using your abilities to farm is fine, but you don't want to be spamming that either. Maybe you should just practice on farming under tower if you are getting pushed in. A melee typically takes 2 tower shots at full health and then one auto will finish it off. For casters, you have to auto the agrrod minion once, then the tower shot will hit it and leave it with one auto attack of health left, and you finish it off. Only use your abilities to farm if you're going to forsure lose that minion. I understand trying to explain mechanics like that is hard through text, but maybe you'll see what I mean in game. Basically I think you should just practice on farming under tower because it is well known LB struggles with wave clear, so you will most likely be getting shoved in a lot.
