Easiest and best soln is a post workout protein shake that has creatine & some kind of fast carb because the window to replenish your muscle is too short for carbs that take long to get there! I use Dextros because its dirt cheap & has very high GI value
Potato (when backed/microwaved ) and white rice both sit high on glycemic index so if you are thinking for choosing between rice & potatos then dont !:) Eat either or both just watch the quantity but thats a given right?
Honestly i prefer grains and starchy vegetables for carbohydrates. Potatoes are a good source of potassium and a descent source of minerals if you eat the skin. I prefer grains and starchy vegetables to white rice any day b/c of higher nutrient content/ antioxidant content. White potatoes have a LOT of starch per amount of weight for their size. So, if money is an issue white potatoes are a good choice, and red ones have even more starch per amount of weight than brown potatoes do. Red potatoes almost get gummy when you cook them they are so densely packed with starches.
For vegetable: potato, squash, pumpkin, legumes/beans, and peas. Grains try:Oats, brown rice, millet, barley, rye, grains that can be classified as cereal grains are what you should be looking for b/c they are loaded with B-vitamins, vitamin A, C, vitamin K also potassium, sodium, calcium, phosphorus, chloride, zinc, copper, magnesium, iodine, manganese, molybdenum, and selenium.(yes, I did look that up b/c i could not remember them all) They are just a healthier option when compared to white rice.
If you choose to use the grains when they are done cooking allow the grains to sit for 10 minutes or so to soak some of the water back up. Some starch and some water soluble vitamins and minerals are dispersed into that cooking water, not that it is a huge deal but why lose them if you don't have to.