How do draw a lewis dot diagram for Ga+ cation

Based on the periodic table you know Ga has 3 valence electrons. (Group 13). But since your cation is positive, it has one less electron (electrons have a negative charge).

So your Lewis Dot Diagram would be the letters Ga+, with two dots next to each other on which ever side of your choosing. So....Ga+: would be a suitable diagram.