We present doping and pressure-induced optimization of superconductivity, particularly focusing on tuning of electronic states in Pd-intercalated TaSe₂ i.e. Pd_xTaSe₂, in which superconducting transition is optimized from 0.14 (TaSe₂) to 3.1 K (x=~0.08) with simultaneous suppression of a commensurate charge density wave (CDW) state. We found that the Pd intercalation can involve a Lifshitz transition in the underlying electronic states at normal states without CDW ground states, which seems to be useful for increasing density of states (DOS) and electron-phonon coupling and in turn two-band BCS superconductivity at low temperatures, albeit its relative importance to enhance superconductivity is not clear yet. Furthermore, an increase of DOS in the vicinity of a doping-induced collapse of a commensurate CDW state can certainly help increase DOS and optimize superconducting transition. Although it was not clear with intercalation, with the tuning of pressure, we found that a second-order quantum phase transition of a CDW transition can occur around 22 GPa, and fluctuating CDW ground states can instigate the superconductivity up to 8.3 K. With systematic Raman and transport results, we discuss how a CDW quantum criticality and related fluctuation can be involved in the process of boosting up superconductivity.