The dehumidifier you get isn't important, BUT you need a good one. There are little cheap ones that will do nothing for you. You will need to spend over $100.
You also need an inline fan blowing out and to open one or two vents on your tent. This will keep fresh air circulating into your tent which will reduce the humidity. Check out terrabloom fans. They're the cheapest ones I could find that work well and I've never had any issues with mine.
I know the cost is high, but the cost of mold is much higher. Good luck!