New ramp ideas.

If you're new to riding transitions I'd say 4' would be a good height, a good 10' wide and a pretty large platform on top, that'll be decent for learning to air a bit and learn some basic lip tricks. Any lower and there won't be enough transition to get air out of. And you want it as wide as possible to give yourself plenty of room going up and back down.
And another grind box sounds like it would come in handy. No smaller than 18" high, then as long as you can get it so you don't have to worry about it never being long enough. The wider it is, the less sketchy it'll feel too

4-6 feet tall would be good to learn on and mellow enough to not be impossible or demotivating to ride.

Like Grumpy steve said, 10 feet wide would be a good start assuming you have space, (or wider if you can and can afford it).

Grind boxes around 18 inches tall are great- you hop 6-8 inches to get on em, just make it like 8-12 feet long is a decent length.

Build a 14 foot tall loop

Thanks for the tips Steve, Dave, and J. I ended up building a box 18" tall x 12' long and the top is 3' feet wide. Top is plywood 2 layers of 1/4". I'm letting the construction adhesive for the rail dry overnight. I've got it the angle iron clamped down proper at the seam. I'll wax it up tomorrow and try it out.

On the quarter I need it mobile so I can move it around. I had a few ideas and I'm going to hold off on it for now. I'm try one of the local skate parks and see what's up. I've herd there are more around theses days. The one I want to try only lets bikes in on Monday. It's what I read on the city website. Something like 600K they said it cost to build it. I'm going to see Monday. I herd there is a vertical half at this park I mentioned. I'm not sure of the size tho