Problems try obtaining images with public gateways. 504 and 429 errors

First of all I want to introduce myself because this is my first post. I am a blockchain developer and I am very happy to find this forum because I have been “struggling” with IPFS public doors for weeks.

I explain you my problem that may be more SaaS inexperience than anything else.

I have a project to sell NFTs in which each user can sell the NFTs he has. These each bring their own gateways, usually public, to access their metadata, ie their JSON files and images.

The loading of the JSON is usually not a problem. But when it comes to image rendering, I get a lot of 504s.

As I am testing I have uploaded to pinata some metadata for several nftS test projects on free account.

With this public gateway, the pinata one, I usually have “too many request” failures.

I have tried many public gateways but I am not convinced by any of them.
In the end they all fail me.

I never render more than 20 NFTs. And I never get a load of everything the first time.

I suspect I have to make these calls in a proper way.

Surely this question has already come up in many other posts but I have not found in any of them an example solution for proper web rendering. sorry for the reiteration.

To finish, I have seen that this gateway publishes:

blocks every 200 calls per minute.

Seems reasonable to me.
My idea is to make one request per second per NFT, but how do I do such a thing?
I’m using React with Ethers.js.

Thanks in advance.