Go big.
You can hold small stuff in a big vice but not big stuff in a small vice, even hold a small vice in a big vice.
I would go for an 8" vice, it is probably the tool you will use the most. Also a 5/8" keyless chuck.
Forget flycutters there are plenty of cheap tipped facemills about - leave one insert in if you need a flycutter ( you won't though ).
Take time to make an accurate datum retaining end stop.
Forget indicator holders - get a lever indicator with a pivoting stem - it will always be set on centre, great for small bores to tramming the head.
A set of R8 sidelock holders will be very useful.
Start to collect a set of reduced shank drills 13.5 to 26 in 0.5 increments and make a stand.
These are items that save me time and frustration on all my jobs.
There will always be stuff you need, so concentrate on what suits your projects.