I have a old road frame with vertical dropouts that i need a tensioner for. THe chain is just a bit too long. I was thinking of trying a half link if i can find one and figure out how they work. I was able to take an old derailleur and make that into a make shift tensioner for now but i cant quite get things centered using the limit screws and it is UGLY. IT makes a fair bit if racket. IM used to whisper quiet. THat said...are any of the $20 tensioners they sell online worth it or are they all junk? Id rather not have my finished build sound like a dump truck backing over a box of cats.
Are you thinking single speed with a free wheel if so Surly makes the singlelator and it works well.
The other more expensive option is to buy an eccentric hub and lace it.
Do not use a chain tensioner if planning a fixed gear build.