I'm a bit confused. Grapefruit, you say you'll keep applying to USNA until the end . . . then say you first and foremost want to be a Marine . . . then say you really want to enlist in the USMC. Those are all admirable paths, but the route you would take for each is very different.
If you primarily want to attend USNA and aren't accepted, your best bet in terms of getting into USNA is to attend a civilian college (see the Sticky above on Reapplying).
If you want to be a Marine Officer and USNA doesn't work out, your best bet is to attend college and go through OCS. As others have advised, talk to an OFFICER recruiter.
If you want to enlist in the Marines because you want to want to be an enlisted Marine, then you should talk to an ENLISTED recruiter. There are outstanding USMC enlisted personnel and it is a wonderful career path for those who want it.
What most of us will tell you is that it is VERY HARD to go from the enlisted ranks to USNA -- harder from the USMC and non-nuclear USN -- and hard to go from enlisted ranks to officer ranks period. There are some programs that offer this, but the odds are long and lot of what is needed will be out of your control. Almost no one recommends enlisting as a pathway to becoming an officer. It can happen, but chances are it won't.
What you can do is enlist and then use the GI bill to attend college. Also, most career enlisted have Associates' or Bachelor's degrees, so there is opportunity to earn your degree while serving.
[As an aside, no one I know who has served "craps" on enlisted personnel. They are the backbone of our armed forces and any smart officer knows that. Can't speak for those who haven't served.]
I know you'd like to keep all of your options open, but sometimes that's hard to do as going down one path may close off others. It is easier to start on the officer path, decide it's not for you, and then enlist than it is to do the converse.