That’s some deep research just to decide on which cards you should invest in. Be careful with the win rate data, it is useful for sure but you have to bare in mind how often will you realistically use those cards. I’m diamond II and I rarely use any of those because they’re niche cards.

Take a good look at your playing style and available summoners. Those are the two most important things to build a deck around. After investing in the “main” cards for you strategy try to buy some niche cards (good for very specific rulesets) to add some depth to your deck. That way you will be able to outplay higher level players that get too focused around maximizing a small number of cards.
That’s the most financially efficient strategy in my opinion.