What present has Gobbo brought to give to Shylock?
The present is food ("a dish of doves"—line 124).
This takes place in Act II, Scene 2. Gobbo has come to visit his son Launcelot after not seeing him for a few years. Launcelot has been working as a servant for Shylock, so Gobbo, wanting to show respect, brings a present for his son's master.
At the same time Gobbo comes to visit, however, Launcelot has just decided to stop working for Shylock. As a result, he does not want his father to give Shylock the present. ("Give him a present? Give him a halter!"—lines 97-98). Instead, Launcelot instructs his father to give the present to Bassanio, with whom he hopes to get a job. When Bassanio shows up, Gobbo offers him the "dish of doves." The doves never make it to Shylock.