Above, we present a list of top casinos with at least a 300% welcome bonus. Bonuses with a 300% offer are always related to a first deposit. Casino make this generous welcome offer to new players to attrack newbies. The height of your welcome bonus is based on your first deposit that you make. So, the more you deposit, the bigger your bonus. I.e. you make a first deposit of €100 then your amount of money to play with in the online casino will be €400. How much of litte real money you have to deposit depends on the casino promotion rules. The smallest deposit in order to profit from a 300% first deposit bonus that we found on the web is €£$ 20.