How big is your pond and how deep?What do you have already? Do you have the plants in pots or planted in the bottom mud.What do you have in the way of oxygenating weed?
Hornwort is very good as you don't even need to plant it,but it grows like mad so you do have to keep it under control.Elodea is good also but soon gets tall and leggy,so break off the top third and repot every year or so.Other plants can be miniature water lilies,or water fringe, but again that grows very quickly.You do need plenty of shade in summer of course to prevent algae problems.
Marginal plants and plants round the edges of the pond are varied and there are many to choose from.Why not see what takes your fancy at the garden centre or get a book on what plants are suitable for various environments.