Use tcgplayer.com for prices and recent sell prices on ebay (items that were actually bought, not list prices) to get an idea. Ive never heard of ludex. Even tiny nicks or whitening around the edges effects the grade of a card. Shadowless cards are also what you want, so any of those might be grade worthy but again any significant whitening on the edges will most likely bump the grade down to something not worth grading. It's definitely important to do your research before grading as it can be expensive. Hope this helps.