You can buy the membership, but I would suggest just searching up on youtube videos about puzzles, like for example this one:
How many chess puzzles

The limit to solving puzzles to help you improve your game is endless. If you want to get better, practice, practice, practice.
I do 5 a day. my puzzle rating has steadily improved from 400 to 1550 since january. if you feel you need more then gold membership is 25 a day which should be more than enough. IMO little and often is better than binging once a week.

Puzzles help reduce blundering. I've found that daily puzzles have improved my calculation and visualisation skills which has reduced my blundering significantly. IMO puzzles are better at developing these skills than playing games. Most beginners need to reduce blundering but dont know how because they dont know why they blunder. The answer is regular puzzles, 5 to 10 per day, aim to get them correct first time, dont guess moves, solve them fully in your head first. After 6 months calculation and visualisation will be much stronger and they will blunder less.

But puzzles do force you to look for undefended pieces. In fact undefended or weakly defended pieces on both sides are a major factor in many puzzles, that need to be accounted for to find the correct solution. But my point was less direct. I'm not saying that puzzles directly help people learn to spot undefended material. My point was that it develops the skills of calculating, visualising and evaluating a series of moves and it is this skill that helps people hang less material. Undefended pieces are a symptom of weak calculation and visualisation skills. I also agree that games help develop these skills so I'm not excluding your idea. However I feel puzzles are more efficient. This is true for many fields, for example a footballer doesn't improve ball control by playing football, they dribble round cones. Puzzles are like dribbling round cones if you'll excuse the analogy.

I'm thinking that the key for me to get better at chess is puzzles. But how many? I have the free membership which gives me 5 puzzles and day, plus a puzzle rush and puzzle battle. But is that enough to improve or do I need more? If so then how much would i need and what membership should I buy?
Apparently more and more chess games is not the key to improvement.
Is there a better strategy is should use?
Well, you can just solve the maximum number of puzzles you can in Chess.com. Then, you can solve puzzles from other websites like Lichess.

If you do tactics in correct way, then it helps you no doubt.
Great! That is how you really learn. I have a 100 game scorebook that I keep my games in. Afterwards, I analyze the games ruthlessly to find the weaknesses in my decision-making process and pinpoint any recurring problems. For example: I was constantly getting in time trouble, so I finally realized it could be cured by knowing my openings well enough so I wouldn't have to spend much time before move ten, and sharpening my calculation and visualization skills.
Unlike online chess, OTB requires intense concentration and focus. If you and your brother could try playing some blindfold chess, that would be great training. I used to mentally solve endgame studies before a tournament. Your victories will fill you with pleasure and your losses will be painful, but both will be memorable and instructive.
We'll talk more between now and then.