Here is an easy way to build a truing stand;
1: get and old fork the will fit your wheel
2: drill a hole on both sides of the fork at the rims edge. Make sure they are exactly the same distance.
3: put about a 4" bolt thru each hole with nuts on both sides of the fork.
4: drop a 2' - 3' piece of all thread thru the neck tube. Use big washers

Tools you will need:
Wrench
Spoke Wrench
Leather or Rubber Mallet
White Grease Pen
... and maybe feeler gauges

Run the 3 bolts almost down to your rim, this is where the feeler gauges space the distance from the bolt and rim. Rotate the rim very very slow to find your bad spots and mark them. Rinse, Lather, Repeat
If you really want to get anal about it. You can wrap small pieces of plumbers solder around the spoke ends, crimp it with pliers to speed balance them.
And that’s how to build a cheap truing stand that you can bring your rims to a thousandths of being true