i highly recommend you get a mouse as it will make your gaming experience way more enjoyable and eazier for you. but if you cant, mess with your trackpad's sensitivity till you find a good sense that you are comfortable with. eventually you'll adapt if you keep playing for a while.
for cosmetics, you'll naturally get weapons which will turn into metal if you desire. look on Scrap or Backpack for some prices on some stuff that would look cool. i'd recommend just buying a key and breaking it down and buying stuff, since it is the fastest way to get cosmetics, and its only $2.49. also never purchase weapons from the Mann Co. Store. its money wasted on things you can get for free.