Thankfully I don't have to rely on three leaf clovers or other gimmicks. Instead I can rely fully on God's word. The Bible is inspired by God so there are no mistakes and He is surely NO SINNER with an agenda.
So why do I believe in the Trinity? Because it is stated in the Bible. This IS ONLY source a CHristian is to rely on for answers.
Matthew 28:18-20
[18] And Jesus came and spake unto them, saying, All power is given unto me in heaven and in earth.
[19] Go ye therefore, and teach all nations, baptizing them in the name of the Father, and of the Son, and of the Holy Ghost:
[20] Teaching them to observe all things whatsoever I have commanded you: and, lo, I am with you always, even unto the end of the world. Amen.
Matthew speaks of the Father, Son and Holy Spirit all being part of ONE name. But, these are three distinct persons.
Deut. 6:4 states this:
[4] Hear, O Israel: The LORD our God is one LORD
1 Cor. 8:6
[6] But to us there is but one God, the Father, of whom are all things, and we in him; and one Lord Jesus Christ, by whom are all things, and we by him.
So God is of ONE essence, but three in Persons. God has one nature, but three centers of consciousness. In other words, there is only ONE "What" in God but there are three "Whos". God is in one essence and revealed in three forms, the Father, the Son and the Holy Spirit.
I dare say this gets to the meat of the matter!
The Bible clearly disagrees with you, and commands obedience both to sacred tradition (2 Thess 2:15) and church authority (Heb 13:7-8, 13:17).
Get back to us when you actually start obeying your "only source" consistently, instead of picking and choosing which parts you want to obey.