If you find satisfaction in making your own graver(s) in the same way most M/L builders find satisfaction in making other parts that could simply buy off the shelf,,then do so.
Plenty of worn but recyclable tools, bits and other steel items make the grade.
Especially when they are going to be confined to 12L14, brass and silver and not the heat treated frames,slides and parts of many of the more modern cartridge guns on the market. Many of those can be miserable to cut.
For the average builder/hobbiest,,keep it simple. Makes it fun. You don't need a bench littered with gravers of all different points and angles to cut.
If you don't want to put the time aside to grind an old file into a graver,,then buy a of packet of lathe tool bits from one of the tool supply places. Usually 5 or 6 to a pack ,,2.5 to 3" long. Take your pick of the fancy steel alloy names. Again,,for the M/L type steels and brass, ect,,any of them cut them like butter if sharpened right.
Carbide is fine if you are up against extremely tough alloys and/or need longer tool life. But a well sharpened HS of any one of the wizzbang alloys should last through most of not all of an average job on a M/L rifle before needing a sharpening again.
There is carbibe and there is carbide. Not all is suited to the impact a graver gets, so certain alloys of carbide work better than others, some not at all for the job. The ones offered by engraver supply houses in tool bit form are pretty well vetted by the engraving community or they wouldn't be on the market as such.
You will need a special grinding wheel to rough out the carbide bits,followed by a diamong faced polishing rig of some sorts to finish polish them. A ceramic wheel and diamond paste does the high luster shine to the points. It not only puts the brilliant polish to the carbide (or any other steel),,but the better the polish on the point on carbide, the less chance of it fracturing. Think glass.It's brittle and any scratch is a stresspoint where it can break easily.
So make or buy what you think you need. You don't need much in the way of a special space age steel alloy to engrave. Just something tougher than the surface being cut.
The real secret, if there is any, is in the actual sharpening of any of the tools.