I am working on my final year project. It is a web based system that is based on ASP.NET/MVC. I want to start from database but I have a little confusion which database to use from Sql, sqlite and sqlite3 that is not complicated and good for me to finish my project on time. can you please give me your suggestions which database should I choose?

ASP.NET works very well with MSSQL. If you are developing with Visual Studio, you can integrate MSSQL very easy. You aren't limited to MSSQL, you can use MySQL or anything else you are comfortable with and that provides you with the proper DLL(s) to integrate with ASP.NET.

ASP.Net will work very well with MS Sql Server.There are definitely some benefits to using SQL with ASP.NET, since the two are architecturally synchronized. However, plenty of high-performing applications use Oracle.

You can use SQL Server Express Edition or MongoDB or mysql. All of them are free to use. But Practically speaking go for sqlserver as it fits best with Microsoft technologies.