Welcome to build land, you are going to remain so far ahead of the curve if you stick with it, it will sicken you with how quickly you will advance, just because you make your own planes.

I'm very old school as a builder, both scratch and kit, and this part of the hobby is so, so much fun, you are in store for more then you realize in that matter.

Now, staying strictly old school, start out with chuck gliders, my material of choice there is foam plate stock and a hot glue gun to assemble it. You'll end up with some fun little planes to kick around the office or shop, but you will also learn a great deal quickly as to what proper dimensions to make everything at. What I've found, when thinking totally out of the box, I've defied traditional design parameters themselves, I've also been able to totally fine tune a pattern to use as a base for the full scale rc version as well. A favorite of mine in that arena, it takes use of the shape of the plate itself, a circle, that is the depressed, flat area of the plate, add a fin and something to get the COG correct, and you have a nice little chuck glider in seconds. Other planes, you really see what you are in for, for example, I did a p51, and it was tough to set the cog correctly, and when I did, it was not always stable, ie. that's why they designed it that way in the first place, to be manueverable.

Staying old school, the next stage I suggest getting a few balsa free flight kits under your belt, supplementing them with what ever you can find off of the shelf to build from scratch in the chuck glider, or free flight electric if you want to be more aggressive about it.

Once you are used to getting these free flight birds flying along fine, knowing what you are doing, moving onto RC will absorb everything you know, but now, you are thinking of control surfaces and additional hardware. It's not a huge transition, but it's one where you want to think more robust with the materials and design parameters, for a free flight plane cannot handle the extra weight and intertia from the gear inside.

When you have reached into the area, where you can build with impunity, then this part of the hobby really becomes fun, including with the pocket book. You have just circumvented the traditional, arf/rtf scene, you make your own replacement parts, and you fly what you "want" to, not just what you are ready for, or planes that are going to be too expensive to own and maintain, much less risk actual flight with.