We now have better ISO performance than we had years ago, so "flash power" is no longer what we need like we did in 1985.
Basic lighting studio? Hardware? Well...150 Watt-second monolight flash unit, like the $99 FlashPoint 320M monolight. A 7- to 9-foot tall light stand. A 34 to 40 inch umbrella light modifier. Maybe a 28x28 inch square softbox. Big reflector card, like a white, foam core "poster board" for a reflector. A second light stand and some type of clamping system to help hold the reflector in place.
THAT is ,"the basics"...you could add a second light unit of the same power and brand, as the next-best accessory. That would require a third light stand, by the way!
Other things: 10-degree honeycomb, grid for a 7-inch reflector, or a three-grid "set" (
Adorama sells this). 7,10,20,35 are the most common degree ratings for honeycomb grids. 10 and 20 are very useful!
Barn door set: 2- or 4-doors, for your 7-inch diameter or "standard reflector".
Better light stands! Boom stand with boom arms and counter-weight; very handy.
More reflectors. Posing stools (2). Background paper system.
More light modifiers: 32-incH and 30-inch umbrellas work a LOT like a beauty dish. Larger, 45 to 48-inch umbrellas and umbrella boxes are very usable in many places.
42x60 inch softbox.
3rd,4th,5th lighting unit.