You may as well enter the ballot as the odds are not great. There are about 17,000 ballot places and last year 250,000 applicants for those places. If you are successful you can defer your place once if you wish. So the places are like gold dust.
Alternatively, if you can run sub 3:05 by this summer you can get a place on good for age.
Finally, and this is not realistic advice for next year, but if you are a member of a club and run sub 1:15 for a half you can get a championship place and enter relatively late in the game (the January before the race). 1:15 takes serious dedication and training - but if you ran 1:35 in your first ever half you could get there with a few years' work.