I will chime in and give you guys some advice. I have a lot of experience with Corbin. I own one hand press and 3 hydraulic presses from Corbin and unreal amount of dies and punches from him. I have .177, 217, 218, 219, 223, 2495, 250, 308, 309, 257, 338, 375, 357, 358, 401, 408, 457, 458, 498 and 510 plus some of these I have multiple nose profiles and a lot of these calibers I have the two step method of hollow points and the one step. On top of that I have many, many punches to make different bases and HP tips.
First you need to decide what HP type you want to make. You can make them in one step or two steps. The two steps you make the core with the weight adjusted in the first step and it turns the core into what looks like a whiskey barrel cut in half with straight walls and large empty cavity in the center. Then you change dies and place that core into the new die and press it in the die far enough to shape in into the slug you are making. This way is more time consuming but will give you the largest HP cavity possible.
The other method is to use a one step die. These dies are more expensive to buy however you only need one die. The other advantage is the die makes the bullet in one pass, bleeds the lead off for weight and forms the HP and nose in one pass, so you make twice as many bullets per hour. The down side is the HP cavity is smaller. However, that is also a good thing as the two step hollow slugs do not have as good of a BC as the one step solid slugs do.
If you want to sell slugs, I would buy the two step method. Most of the larger companies will be making the single step method so you can fill a niche. I could make the two step style slug on my new machine but I don't have immediate plans to do so and may never do so. You can make a smaller cavity in a two step by using a smaller pin if you want the ability to make a larger cavity or a better BC version in the two step dies.
As for size you have to know what your guns wants. It should be obvious what most guns shoot, look at what is on my website, they are not there by accident. No die you get will work in every gun. I would get a dish base, flat base and cup base. You will see flatbase will work in most guns but not all. Some guns will want a dish base or cup base. HP base almost never works, maybe if you use the two step HP method.
If you are going to use wire, get Corbins wire cutter and mount it to a bench. Corbin's wire is very good. I don't like Corbin's swage lube. Although I use a special lube I used to use Slick 50 in a can and it worked well. Use very little lube but you must use lube or you will lead up your dies. Buy his S Press, a reloading press will suck. You need the leverage. Corbins equipment is very well made and they are very good people to deal with.