Portioning both wet and dry cat food daily for new cat?

[CaseysHuman]

I adopted my cat Casey from a friend of a friend just 3 days ago. I've never had a cat before, so I'm unclear on quite a few things and I wanted to see if anyone can help me.

Casey is 10 years old, and he looks like a domestic mix of breeds. He has a medium length white and grey fur with a pink nose and yellow eyes. He's a very quiet friendly and self-sufficient cat, and he does basically everything by himself as long as his food and water bowls are full and his litter is clean.

I was given a bunch of dry kibble food and several cans of grain-free Wellness wet food from his previous owner and was told that he eats both and that I should give him half a cup twice a day.

I wasn't really sure what that meant in terms of the daily wet/dry food portion ratio.

The first day he ate a little over half a can of wet food and a half-cup of dry food and he peed once. The next day I gave him a half-cup of dry food to start with. That lasted him the entire day and night. Again, he peed once during the night. This morning he woke me up at 10am. His food bowl was empty, and when I fed him half a can of wet food, he wolfed it down. He hasn't asked for more yet, although I'm sure he'll get hungrier later.

Am I doing this right? I've had him for about 52 hours so far and he hasn't pooped yet. I've heard that cats pee 2-3 times a day, but he's only gone once a day so far. He appears to be healthy and normal and he's not acting strange or anything. He also drinks water regularly, especially after eating kibble.

Should I give him more wet food? Should he be peeing and pooping more often? I haven't taken him to the vet yet, and his owner hasn't replied to my emails.