leethomas,
We are glad you joined in here---we always have room for one more!
We're sure not going to beat you down and force you to wear low-power training wheels, but jumping straight to mid-power can be a pretty big first step.
F-powered models can sort of straddle the range between extreme low-power and introductory mid-power rocketry. If the rocket is (relatively) large and heavy, it will not accelerate as severely with an F motor, and low-power construction materials and techniques may let you get by. OTOH, if your F-powered model is (relatively) small and light, you are going to need to learn some more about advanced building materials, adhesives, and techniques if the rocket is going to survive the launch, ejection, and recovery.
It would help you a LOT if you could find a local club, where you could see some of these things in person, and where you could get good advice. If you don't have a club in driving distance, I would suggest you start with low-powered models. For one thing, you will have a lot less $$$$$ invested in the rockets, motors, launchers, etc, while you make a few first launches.
Don't make the mistake of thinking that a C or D-powered rocket is just a "kid's toy" because some of these will perform just as well as many mid-power designs. If you build a low-power rocket properly it will be light, and a D (or E) motor will take it pretty high. A corresponding mid-power rocket will often be built of more durable materials, but this also makes them a little heavier, so even with an F motor, a mid-power rocket can sometimes turn out to be slower and lower than a lightweight low-power model with a D or E motor.
Take a look at Estes' Blue Ninja, or Stormcaster, or Big Daddy. These will take D motors, and can still use 18mm motors if you use an adapter. Some are already designed for Estes E motors, or can easily be modified. And there are other low-power rocket designs from other vendors that will also perform very well for you.
Starting with Estes-type, low-power rockets will get you started with launch pads and electrical launch controllers that are easier to master, motors that are much easier to find (and cheaper), and igniters that are easier to get the hang of. Many Aerotech mid-power motors now come with improved igniters, but if you happen to get hold of some "old stock" with "Copperhead" igniters you may have a few problems (and learn why many people called them "Crapperheads"). Starting with Estes-type rockets is not really such a bad thing.
If you want to try mid-power right off the bat, you need to know that if you also start off with a nice kit and a reloadable motor system (RMS), you will spend a little chunk of $$$ that could end up drifting away unless you very quickly learn how to compensate for winds aloft. This is another place where low-power rockets can come in handy, because you will want to begin your launch with one or two flights of less expensive rockets to see exactly what the winds up there are doing that day.
Do come back here often to TRF and ask more questions. There are lots of folks here willing to share experiences and opinions, and they can point you to places where you can save money, or safely cut some corners on your way to mid-power operations.