During the Ginga Patrol Jaco, probably no more than 500. He stated that even the Ginga Patrol were no match for Saiyans and even Raditz is an elite Saiyan according to Toriyama's interview in the Chozenshuu.
In FnF, he was able to trounce a few of Freeza's soldiers, though many of them were likely weaklings and his ray gun played a part according to the summaries we have. I wouldn't really place him much higher than 5,000.