7 decks too much?

Seven decks with the amount of cards you are planning would be a total of 450 cards. It would obviously allow for diverse game play, but the production costs (including board, box and shipping) would seem prohibitive, particularly for your first game. I suggest creating a simpler version or a variation, just to get a feel for the whole process. Coming up with a great idea and developing it into a viable game is just the first part. Artwork for cards and box need to be prepared, rules need to be scrutinized, refined and proofread. Then you need to secure funding, find a manufacturer and devise a marketing strategy.
A great place to start is:
https://www.thegamecrafter.com/
I have just posted my first card game "Planet Pioneer" for immediate sale there:
https://www.thegamecrafter.com/games/planet-pioneer
It is a 90 card deck, with 11 different cards. It was a learning process and involves a bit of work, but a very worthwhile resource for up and coming game designers.
Cheers!

My first game design is Crazy Pipes it's a strategy game played with dice. I had a similar problem it uses 82 custom dice. The best price I could get was 35 cents per die that would place the cost of just the dice at 30 dollars. It also requires a board. Obviously that would be quite expensive. I kept looking around and it has taken me 6 months to find a manufacturer that I could get the price point I like. Problem is volume. I don't have the money to afford the volume at that price so I am going to use kickstarter. I'm not spamming or advertising. Just running a course of action for you.

Sometimes patients pays off and you just need to keep looking for what you need. Everyone loves to play my prototype and it will be a great item when I get to that point. I have lots of steps to go.

Basically I'm saying that yes that is a lot of cards but if the game plays well and people like it keep moving forward. Price is always and issue.