Wheel tensioning and truing can be tricky. My experience is with bicycle wheels, but the concept is the same.
It's not enough that all the spoke tension be equal; that won't necessarily true a wheel. The tension has to be applied in a sequence, in small increments, while measuring the roundness and runout. The wheel not only has to have the correct runout and round, but the hub has to be in the proper position in relation to the wheel (that's called the dish). Sometimes when you try and bring up the tension of loose spokes to match the tension of tighter spokes, without doing any other adjustments, you can actually pull a wheel further out of round or out of true. Ideally, when working on a wheel, you try and start while roughly equal tension all around, and then work your way up to the proper tension while also adjusting the position of the wheel in relation to the hub.
Before you mount a tire to the wheel, I'd make a jig to spin the wheel off the bike, just to get an idea if the runout and round were okay. You can put the axle through the wheel, then balance the wheel and axle on a couple drywall buckets (or anything that'll allow you to suspend the wheel so you can spin it freely). Spin the wheel and watch if from the front. If you see the wheel wobbling top to bottom while it spins, then it's out of true. If you look along the top edge of the wheel while it spins and it seems to be "hopping" (you can see a high spot keep appearing as the wheel spins), then it's out of round. That's a really rough way of determining if the wheel is true; there's actually a specific allowable runout on the wheel that's pretty small. You might not even notice it visually, but if you can actually see the wheel hop or wobble, then it's definitely out of round and/or out of round, and it's time to take it to a shop that knows how to true a wheel. I've had some experience truing and tensioning wheels, and I still took mine to a shop when the runout was too much to have someone who knew what they were doing fix it.