Beginner: What Tech stack for a simple RAG bot?

I wanna build a simple rag bot for my website (Next.js). Reading left and right on where to start and there's so many options to choose from. Perhaps someone with experience knows something good for a beginner to build their bot with, what vector db to use and also keeping it free/open-source? I might ask wrong questions so I apologise but I'm bit lost on what tech to study or start from. Just asking for your opinion really... thanks. One thing I've read alot is to not to use LangChain I guess.