Hello again!

State revenue is difficult to parse in pre-industrial societies. In the monarchies of Europe, there's seldom any distinction between the personal income of the monarch and the income of the state (l'etat c'est moi, after all) and a similar practice held true in Italy, where the dominant construct of political organization (the Comune) was not conceived as an entity separate from the body politic.

This means that across Italy, every public project from gatehouses, to bridges, cisterns, and even war, had to have someone commit to paying for it beforehand.

Predictably, systems varied from place to place. In Florence guilds (and later mercantile dynasties) splurged to transform member dues into public works, while in autarchic Milan political dynasties were charged with constructing public works in exchange for privileges (until one dynasty trumped the rest). In Venice all sorts of schemes were drawn up to pay for public works, either raising money from the neighborhood who would use the public good in question (bridges and cisterns were typically financed in this way) or relying on the largesse of one or more wealthy patrons. When taxes appeared in Venice they were typically one-offs, raised at the start of military expeditions or great public works like redirecting rivers. In later periods a system of public coffers did start emerging but revenues remained small, typically manifesting in the form of tolls and duties. Concurrently with the evolution of Venetian finances mandatory loans emerged as a favored way of raising money, but these too were only ever one-offs applied in extraordinary circumstances.

Participation in Venetian government, for all its councils and committees which would only grow more complicated over the centuries, was always voluntary. To its very end, political office came with no explicit monetary compensation (and this might have contributed to the Republic's undoing, as in the Late Republic destitute aristocrats were more than willing to sell their votes). Indeed, this is why the Venetians were able to guarantee, at minimum, a seat in the Great Council for every single aristocratic citizen. While it did not offer direct compensation, what participation in government did offer was, in the Republic's initial period, a space to air grievances and settle disputes, and in later periods participation in Venetian government allowed leading citizens to not only agree on rules and regulations, but also in collaborate to steer the Republic's economy. This occurred most notably (as you correctly mention) in setting the specifications and timetables for the grand trade convoys which would set out from Venice across the Mediterranean. These convoys (called Mude, more commonly appearing in the singular form Muda) were only financed by "The Republic" in that the Republic's senators and councillors were the ones paying for them, and predictably the ones who stood to gain the most from them.

There was a similarly personal approach to the Venetian's mainland and overseas possessions: Consoli in overseas possessions, or Podestà in mainland possessions, were typically Venetians who already resided in their community and who could expected to govern in their own interest (typically mercantile interest) and by extension in the interest of the Republic. There were of course nuances, as the Venetians also typically left preexisting local political institutions intact, and Venetians also had a habit of guarding their overseas possessions with fortresses defended by small companies of salaried soldiery, paid for by local tolls and customs duties. But this was typically the maximum extent of the Venetian state. It is only in the very late life of the Republic that a small public administration indeed began forming, typically paper-pushers appointed through patronage and tied to the appointment of councilors of the offices of state who remained, to the end, unpaid.

Thus when we talk about the strength of the Republic of Venice, we are really talking about the strength of what the Republic's citizens were willing and able to come together in order to achieve.