You could start by spending some time here and reading other peoples reports some of which contain a list of what they carry.https://www.crazyguyonabike.com/
If you are on a budget a second hand quality bike might be a better buy than a new one for the same price, you might even get one with racks, panniers and other useful equipment included. In my opinion the most important components are the seat, chain and tyres, for the latter most people seem to use something from the Schwalbe marathon range which I have found to be excellent.
Start by doing short trips, even one night away to get used to what you need and how best to carry it, you will get used to managing with very little on a bike.
Good luck with your planning, cycle touring is a great way to see your country and the wider world.