I agree that you don't have to "overthink" it, but there is a fair amount of thought required to get it right and make sure your aren't wasting your money. Fertilizer and seed isn't cheap these days.
In VA we get soil sample boxes and the associated forms at any public library or cooperative ext office. Wildlife food plots are considered commercial crops so the soil test is free. You just have to pay shipping. A few days after Virginia Tech receives the samples they email you a PDF with the results and recommended lime and fertilizer amounts. Being an agricultural state, I'm sure IL has an identical system.
Soil Test The field in the above soil test is about 1/2 acre, so we needed 2.4 tons of agricultural lime and four 50lb bags of 10-20-20 to get to their recommended levels. That put us a tad short on nitrogen so we hit it with 1/4 bag of 34-0-0. We put the lime down back in March, and fertilized and seeded last weekend. IMO, the lime is the most important step because if the soil PH is too low, the plants can't use the nutrients efficiently and you are just wasting your money on seed and fertilizer.
For the fertilizer amounts, you can either do the math, or use the very good and easy to use online fertilizer calculator on the Texas A&M website.
Fertilizer Calculator A 50lb bag of 10-20-20 contains 10% nitrogen, 20% phosphorous and 20% potassium, OR 5lbs nitrogen, 10lbs phosphorous and 10lbs potassium. In other words, half the bag is actual fertilizer and the other half is inert filler, yet somehow they can still justify charging you $18.00 per bag for it......
I had really good luck this summer with Hancock's Spring and Summer mix on that powerline even though the soil PH was low. I didn't want to wait for the lime to work so I limed, fertilized and seeded all at the same time and it worked out OK. This weekend I'm going to re-seed it with Hancock's Fall and Winter Mix. I also get my buckwheat from Hancock Seed, mostly because they have free shipping for the 25lb bags.
This past weekend our club planted 6 fields we've been prepping since the spring, so I can't make any seed recommendations yet, but we used the following seeds: Deer Creek Seed Wildlife Clover Food Plot Mix, Wildlife Perfect Wildlife Brassica Mix and Wildlife Perfect Wildlife Grazing Mix. We picked those specific mixes because they had a lower PH tolerance than most of the others. We also mixed 10% brown top millet from Hancock Seed into them - 1) as a nurse crop and 2) to maybe bring in some turkey and dove later in the year.
I'm also prepping a small plot in the woods by one of my stands and I'm going to try the Deer Creek Seed Logger's Trail Mix. I'll be using 2 bags of Pennington Fast Acting lime to hopefully bring the PH up quickly. The fast acting lime is 4X the cost of regular lime and doesn't last as long, but it works a lot faster
