At the beginning, I would occasionally buy a few of the 0.99 premium scratch tickets from the Kwik-E Mart. After a few months of still not being able to get the things I really wanted, I began buying donuts. I have twice purchased the boatload of donuts and once the store of donuts. I have been able to use the monorail tasks, Where's Maggie game and daily tasks to help in little spurts.
Once I started coming to this board regularly and began to understand the mechanics of farming Kwik-E Marts, Bloodmobiles, and Rat Trap Trucks things got way better. For the last few months, I have been able to keep my donut reserves between 1000-1500 donuts at all times and I get "most" of the new premium things that I want.
Read the Tips for New Players & Other Links stickied above written by Muhsterino. It is invaluable.
Have fun and good luck donut building!