It's all about looking at the outcome, set goals and stick to them. Try to make friends and it will motivate you to keep going. Probably the hardest thing about any sport is dedication.
28-30miles really isn't a lot depending on the actual route. I mean 30 miles on flat ground is really not a lot at all. 30 miles of climbing can be. I usually only put in about 20-40mile days that usually are all climbing with a faster group. Then once every week I try to go for a long flat ride. Usually 60-80 miles. If you've got any hills/mountains near you take advantage of that. Probably one of the quickest ways to become a stronger rider is climbing. Of course you want to do some sprinting and flat ground riding as well.
Really don't worry too much about mileage right now. What your goals should be is getting out there consistently and riding with people faster than you. Yes, you will get dropped, don't let that discourage you, just keep going out there and keep pushing and eventually you'll be dropping them.
Try to mix it up a little bit, plan at least one LONG ride every week. You want to build up your mileage slowly on your rides. Say for example you do 30 miles this week, maybe next week try adding in another 5 miles. Then continue this. If you feel you need to take a break one week that you're beating your ass into the ground take it easy and go back down to 30 miles for just that week.
If you haven't figured it out already, another key to cycling is proper hydration and food. Have you bonked (hit the wall) yet? I remember the first time I did, 30 miles from home and I bonked. Basically your body just gives up, runners call it hitting the wall. You feel sick, sleepy, your muscles just don't respond and it is near impossible to move on. How does this happen? Not from being out of shape, but because you're not eating properly. You need carbs, electrolytes, and water. A rule of thumb for water is 500ml every hour. Of course that can vary from person and temperature and that's something you'll eventually figure out on yourself. Bring something small along with you to nibble on that you know won't upset your stomach or weigh you down while riding. I'm a fan of cliff bars, they're easy on my stomach, taste good, and you can find them anywhere. I also like their Shot Blox. The margarita ones are good.
Eating really depends on the person, for me two cliff bars will do me fine for a 60-70 mile ride. So you're going to just have to experiment with both drinking and eating to figure out what works best for you.