I would also like to point out that shorts isn't where you want to go cheap. If an expensive pair is what will make longer rides comfortable, it's worth it. I don't really have a reccomendation because in my experience, your body, your saddle, your position, and other factors, all make a difference. My current favorite bibs are from Pactimo but they are pricey and I only buy them during sales.
I also recommend buying from a smaller company that is dedicated to cycling clothing. I think their products are more consistent in terms of fit and quality than big companies like PI that might just be buying whatever outsourced stuff is the least expensive. Pretty much every brand has certain seasonal sales where prices are reduced considerably; like 30-50%.
One other thing that should be mentioned is that whatever saddle you have may not be right for you, in which case, cycling shorts/bibs may not help much. When I got back into biking, I bought a used bike that had a Prologo saddle that was supposed to be pretty good but not for me. No matter what I wore and how often I rode, it was bad. 20 miles was hard, 30 was painful, and after 40 about all I could think of was how much it hurt. Once I found a better saddle, I was able to increase my riding substantially.