There is the official Pokmon Trading Card Database, which will help you spot any text or stat differences, but isn't great for differentiating colors (since your monitor may not precisely match the colors a printed card would appear in your room), and of course it can't help you with determining the feel of the card
Latias #105 (Pokemon Japanese VSTAR Universe | Pokemon Cards) prices are based on the historic sales
Different Vampire cards play off different aspects of this mechanic: some help create Blood tokens, some add a little bonus when you sacrifice them, and some even offer alternative ways to spend them
Collecting signature cards will unlock rental decks as usual, for example, while piecing together the entire set slowly but surely will unlock Dialga and Palkia icons
Beginners should stick to basics: understanding card values, keeping an eye on market trends, and starting small