The right instrument is the one that shows the signal you don't understand yet. Budget pocket tools and a logic analyzer catch most digital bugs before a bench scope is necessary.
Over 120 parts spanning pocket oscilloscopes, logic analyzers, RF and semiconductor analyzers, multimeters, soldering tips and consumables. DSO Quad and Miniware's 4-channel scope cover waveforms; Kingst LA5016 and ScanaQuad handle logic capture.