I did a tour of S Ireland in a Raleigh Pioneer rental bike.
I know plenty of people who tour on low end bikes. The Raleigh is about the lowest grade that is usable, and I would have no problem using one again. What style of bike is yours (MTB, hybrid?).
Work out the cost of the upgrades to make your bike more reliable:
There are some components which could be usefully upgraded. The bottom bracket should be exchanged for a Shimano UN52 (standard, reliable cartridge).
The wheels should be checked and tuned by a good bike shop. Make sure you have good kevlar-banded touring tyres (Continental Top Touring, Schwalbe Marathon).
You find that rear panneirs are enough. I have a cheap copy of a Blackburn rack that is very good. There are ways to fit a front pannier if you dont have the threaded eyelets halfway up your fork blades.
Start the tour with new chain and good quality brake blocks.
Compare this with the cost of a fully kitted out new tour-worthy bike. Depending on the country, this may be called a trecking or hybrid or touring bike. Giant and Treck are two companies that are found everywhere , but smaller no-name brands are often better value.