Also (this is possibly common knowledge but) your credit score is negatively impacted not just by % of available credit utilized, but also by average age of credit accounts. If you're going to want a significant loan (eg a mortgage) in the forseeable future, something to keep in mind.
Not endorsing, but these are the ones my "newsletters" email account subscribes to:
* https://yourbestcreditcards.com/ for credit card bonuses
* https://www.frequentflyerbonuses.com/ for hotel, airline and other travel programs
Credit score is impacted by the average age but tbh, I've gotten two mortgages while doing this and compared the numbers with my peers and it could be my situation is unusual but the "cost" was like .2% APR between those that don't churn in my RL group and those that do.
It has (in my experience with multiple mortgages) have a rate set by competent use of credit that does not lead you to have much debt but paying regularly in practice regardless of what the public credit score algo is telling people.
Overall Chase business cards seem to usually have the best deals, and they don't require you to have a "real" business to get them.
It does impact your credit score, so you are correct to be careful if you're going to get a mortgage soon. But in my experience, the effect can't be too big because my credit score is still excellent despite getting a new credit card every couple months.
https://johnnyafrica.com/multiple-chase-ink-business-cards/
With Amex it’s even better. Once you have one credit card with them, they usually don’t even run a credit report. That means you can then sign up for business credit cards with no effect on your report.
As far as websites,
The current hot offer is the 100k points signup bonus for the Chase Sapphire Preferred card.