Don't remember, besides it changes every time I restart the campaign. As for size fleet I engage, I try and avoid everything larger than 1, but sometimes a bigger pirate fleet chooses to engage me and I can't seem to do anything about it since they are faster than me.
They shouldn't be faster than you, and if you start with a ship that isn't a Lasher or Wolf, you should sell it off at the Hegemony station to GET a Lasher or Wolf. Personally, I prefer the Lasher.
You should also be able to singlehandedly take fleets of up to 3 units comfortably. Some advice regarding fighting multiple opponents:
1) Isolate! Pick the squishiest enemy, and go for them first. In my experience, in regards to the pirate fleet, this usually means going for the Hound or Buffalo, since neither has shields. A few harpoon missiles will sink a Buffalo, but don't use your missiles on the Hound, since they're usually too fast for their own good. The logic here should be obvious, you're fighting 1v3, so you should attempt to even the odds as quickly as possible.
2) Autofire! If it's a turret and not a missile weapon, it is probably a good idea to set it to autofire. This isn't about questioning your aim, it's about pouring on as much firepower as possible. Since you can't shoot more than one weapon group, let the computer handle as much as possible.
3) System map! Look at your system map (TAB) FREQUENTLY! Don't get caught off guard, and if things get dangerous, fly back to the Hegemony station. Sell all the fuel you get for free money, and make sure you have a decent number of marines for boarding. Early on, this is how you'll get more ships.