Oh god, a few dollar investment on a mouse would be a good idea you know =^= And if you got yourself really into osu!, you would want a tablet sooner or later too :^) Anyways, welcome to the forums and I hope you enjoy the game~!
Used to be a trackpad user myself, mate Props to you for sticking it out so far, although I wholly recommend getting a mouse or tablet. You'll thank yourself in the long run haha