I mean, the answer that /u/finuke provided is correct, for the most part. Although Florentine companies conducted business during the 13th and 14th centuries, it never had a port of its own until the Medici acquired Livorno in the 16th century. By that point, however, even if the city had access to sufficient timber to build a navy, it did not have the wealth to contend with the Spanish crown, the Ottomans, and the Venetians. Tuscany did produce Pisa, which did have a more limited Mediterranean colonial empire, but never recovered from the Battle of Meloria. Both Venice and Genoa had ports, access to sufficient timber, and began sending navies out over 500+ years before Florence even had a port.