Forget carbides and all that crap and just use good quality high speed steel.
M34 or colbalt comes to mind.
The cheap m2 stuff is passable if anything.
Get some good tool holders and a fine grinding wheel and have at it.
1/4" tool steel is all you should need for 90% of all the work you will ever do.
What you lack in linear feet per minute you can make up in depth of cut.
You can thank the old machinists later.
A few tool holders and you have about any thing you can imagine.