Water infiltration and dehumidification are separate topics.

Mandatory to prevent the former at all costs. The latter depends on humidity level, which you can *easily* measure to determine the need. Do it.

I've lived in a house or two that needed a dehumidifier in the basement, and my present one has never needed one. No idea why the difference.

Is your basement conditioned space? Meaning are there supply vents for heading and cooling?

We run the dehumidifier certain times of year, but not all the time. It's a portable unit.

If you live in the South where there is high ambient humidity, you may need dehumidifiers in the basement, crawl space or the main home.

We have a sealed crawl space. When we bought the house, the humidity in this area was in the 70% range. Our HVAC guy installed dehumidifiers in the crawl space and the home. What was a potentially very sick house became a great home. We check the humidity levels regularly and they are in the low 40%. Mold can't grow at that low a level of humidity.

If you already have mold problems, along with dehumidifier installation, have your HVAC guy look at https://gpshvac.com/.  In combination with our dehumidifiers the GPS system has cleaned the air in our vents and home. My allergies are so much better.

New homes have soooo much moisture. I am in a new home too (with full unfinished basement) and while my basement does not feel at all damp to me our builder told us to run the furnace fan at least an hour a day for 6 months to help with this. I would have to look at my paperwork but it has on there how much extra moisture would need to “release” from new home in first year or so.

We finally got our AC installed this week and it has a built in dehumidifier and our basement is a conditioned space. But we also added a separate humidifier for winter months. Fun of living in a true four season climate!

Leaks are a totally separate issue. I hope those are fixed and you don’t have any more issues. A leaking basement is a massive headache, especially a brand new one. I’d recommend hiring an independent inspector to check moisture around basement walls and so on so if it needs to be fixed it is soon and on builders dime, not yours down the road when the problems become more visible.