To get a fuller pot of philodendron, you should start with many cuttings in a single pot. Having a pot full of philodendrons will help you achieve that fuller look. Also, give your philodendrons bright and indirect light and fertilizers to help them produce bigger leaves. You should also prune your plant to encourage it to grow more. You can always root the parts of your philodendron that you've cut from the mother plant. Another trick you can try is to stake your climbing pothos, so they are encouraged to grow bigger. This Planterina video will explain all of these in greater detail.