I agree with Aquahull and Survival. Look at the positive here...your prepping is already paying off if you've needed to dip into your reserves. That's what it's there for (when you need something to eat and do not have any other means of getting food). At least you had something extra to get you by until payday. However, I know what you mean.
At Walmart, you can get 1-pound bags of dry beans and white rice for roughly $1-$1.50. Every time I would go there to buy groceries, I'd pick up an extra bag or two. Now I have about 50 lbs of white rice and 50 lbs of various dry beans stored up. You can also get salt very cheap, as well. When we had some extra money saved up, then I purchased some mylar bags and oxygen absorbers online (ordered just enought for my rice and beans to begin with).Then I purchased individual cans of soup, canned chicken, Spam, canned vegetables and Chef Boy-r-de over the following weeks (just buy an extra can or two or three when you can.) That is how my food supply started.
Also, the holidays are fast approaching. If you have family members asking what they can get you for Christmas, tell them flashlights, batteries, a weather radio, a propane stove from Wal-mart, extra small bottles of propane, etc.
Most of my stored medical supplies come from the dollar store (The Dollar Tree, Dollar General, Family Dollar). I NEVER pay more than $1 for each item - band aides, medical tape, gauze, Neosporin, anti-itch cream, peroxide, alcohol, etc.
For clothes for the bug out bags, go to the Goodwill, thrift store or yard sales. Most people don't have enough clothes to take away from their closets now. And clothes are expensive enough to buy new for everyday wear. Our BOB needs to contain items that we won't miss or need each day. So you can get the more expensive items - jeans, shirts, coats, etc - used. I also bought extra blankets for the vehicles from the Goodwill.
Hopefully some of these ideas will work for you, too. I understand how frustrating it is getting started. You want to buy months' worth of everything from the start. I am still a very newbie prepper and after all these weeks have finally accumulated one month's worth of food and water. Hang in there and know that you are not alone!