Reels are still the best for reaching new people because Instagram pushes them to audiences who don't follow you yet. But regular posts and carousels are great for building trust and giving your existing audience a reason to stay.
My strategy is usually simple: use Reels for discovery, carousels for education or storytelling, and Stories for building relationships. Growth comes from understanding what your audience wants to see, not just posting more.
For website conversions, don't just sell. Create content that solves a problem, builds trust, and gives people a clear reason to click your link. The accounts that grow fastest usually have a clear niche, consistent message, and a strong reason for people to follow.