yes, hard woods are best. Boiling them is a MUST though (I'd do it twice) and I believe they should be hard woods. You can also use large rocks (after cleaning) that you might find.
One of the keys to getting a nice looking set up in a tank is balance and the rule of thirds. Essentially it is how to lay things out so the look pleasing to the eye. This article
is a great help, though you have to put in the time to read it. I have successfully mixed plastic and real plants, so if you are on a budget, work with what you have. I do prefer more natural looking plastics though. Also keeping the outside of your aquarium glass clean and streak free can really help. I recommend using vinegar and water because it will not harm your aquarium if a little sneaks in while you're cleaning, or spray your paper towel in a different room and don' go all the way to the top edge to be on the safe side. Really just use vinegar it works great. Hope this helps good luck! You can make really beautiful scapes on a low budget if you look around you and shop smart (thrift stores can be great, if you are patient or lucky!).