What lighting techniques help two-light indoor portraits with modest gear?

[Victoria34]

I'm an amateur photographer trying to improve my indoor portrait work, and I've hit a wall with my basic two-light setup. I understand the concepts of key and fill lights, but my results often look flat or overly harsh, especially with my limited space and budget lighting equipment. For portrait photographers who started with modest gear, what specific lighting techniques or simple modifiers did you find most effective for creating depth and a more professional, flattering look without a full studio setup?