When I get a new to me machine it gets cleaned and lubed. The top tension is usually removed, disassembled and cleaned, then reinstalled and adjusted according to the instructions in the TFSR site along with the tips from ArcaicArcanes blog.
The bobbin case, hook assembly and that entire area is cleaned thoroughly. The bobbin case especially. Then adjusted.
It's not that hard. If it's got you frustrated, take a break and come back to it later.