Scott, number 4 or 4 1/2 stanley or record is a solid first choice, next would be a jack no. 5 or 5 1/2. If you look around you might just get both for your budget. The 4 1/2 and 5 1/2 have wider blades and are heavier planes and take a bit more effort to use.

If you are going to use predimensioned lumber aka pine from homedepot etc then a no.4 is really all you need atm. As you grow in this endeavour your going to eventually get several planes and a jack plane in either size is likely to be your second when you start using rough sawn lumber. Next would definitely be both a router plane and a plough plane.

Your sharpening system is sufficient but I’d suggest making a strop ( 3 inch x 12 inch piece of leather glued to a piece of wood. Charge it with chromium oxide and your good to go, it will polish your irons and take them to another level of sharp.

Refining the old planes is a fun and you can get these old tools to work beautifully. I just have to show this photo, bought this old Bailey no.4 a few weeks ago and got the iron all tuned up and was playing with a piece of mahogany 🙂