Gnat

Deceptively simple, this model is easy to build and teaches you the basics of trimming. It is also a lot of fun.

The Gnat can be found on the  Project Air website. If you have some balsa and a prop, it can be made directly from the images on the AMA plans  site. The plane is so simple it can be made from this article. 

Don Ross has written an excellent  book  'Rubber Powered Model Airplanes', that includes this model as well as information I still find useful.

Ajax 

Don't be afraid of building  large models; they are more tolerant of minor building errors and fly well. It can be bought as a kit or as a plan.

There is whole page about building here

Covering

Coverings create an aerofoil, protect the model and act as a stressed skin - strengthening the model. Covering can be with tissue, fabric (silk/nylon) or plastic films. Good covering techniques make for a neat model - but probably don't make them fly any better.

Composite coverings, with a plastic film under tissue are described here.

What next?

Once you have built your model, get it to balance, then it is time to commit it to flight - a process we call trimming. This site has a hopefully useful guide.