What materials are you machining?
I make most use of a 6mm diameter, 3 flute and 10mm diameter 4 flute end mills when milling using the vertical slide in my 7x14 lathe - mostly on aluminium, but also some steel. The 3 flute works particularly nicely on aluminium. (I think it's carbide, but both carbide & HSS work OK.) I also have a set of cheap Chinese HSS slot drills that have worked OK when I've needed them.
Choose cutter/shank diameters to suit the collets you already have.
I have a small flycutter (about 40mm diameter?) but the lack of X travel means I've never used it.
(You *need* to be able to lock the carriage, IMHO).
