A great first step is a single off-camera speedlight setup rather than jumping straight to larger studio lights. Several photographers recommend starting with the Strobist Lighting 101 lessons, which are specifically aimed at learning portrait lighting with small flashes.

A budget-friendly kit is:

• 1 manual flash (or TTL if compatible with your camera)
• radio triggers for off-camera use
• a light stand
• an umbrella swivel/bracket
• a shoot-through or reflective umbrella

This gives you a flexible, inexpensive portrait setup and teaches the fundamentals of light placement, direction, and softness. Manual flashes are often the cheapest option and work well for learning. TTL can be convenient, but compatibility matters.

If money is very tight, you can still start with one flash and improvise modifiers: bounce the light off a white wall or ceiling, use a white board as a reflector, or make a simple DIY softbox from cardboard.

In short: buy one affordable off-camera flash and basic modifiers first. It’s the best-value way to learn indoor portrait lighting.