you will need longer to gain certain things as a free player, there are no other differences
you 1st need to gain gold and then with that gold you can either buy desired items from auctions or you exchange this gold to BC (Blue Crystals) and buy direct from the shop
those who pay $ get BC directly for their $; thus they are faster
so you can either farm ingame or you "farm in RL" (meaning you gain $ and buy gamecurrency), do what you like more