I dont' think you can only have one type of boots.
I currently have:
four pillow wraps (sized for fronts and backs)
4 standing bandages
4 sheet cotton padding wraps
4 track wraps (similair to polos, although I prefer these)
Full set of 4 SMB-3's
Two sets of prof. choice no-turn bell boots (4 total)
One set Basic splint boots
One set Skid boots
Keep in mind I ride western though, all the events I do require a lot of leg protection because they are high-impact. (Reining, gymkhana, drill team).
For a flat english horse only though, I would get a set of shipping boots (I don't have these, but use the pillows and standing bandages instead-shipping boots will be easier to handle though for a first-time horse owner) if you plan on traveling often to shows, etc. I would also get some bell boots (if you plan on jumping, or if your horse is prone to over-reaching), and some type of SMB's (Prof. Choice are top-notch and last a long time with good care). SMB's provide the same protection as splints, skids (sort of), and open-front boots. However, I know jumping people do prefer open-front boots so their horses can feel when they hit the bar).
Hope this helped!