First off you need to get to a point where your rep is good enough with the factions so that you don't take a hit on rep, life will go on. So auto-trading illegal goods early game is out. Now that you have the rep, you need something that is going to be able to land 100% of the time without queuing. That would be a S sized ship. If you look at the size of the illegal goods, theres really no need for anything bigger than that anyway. Next you need something that's going to be able to get in and get out fast. You need speed. Take some time to examine the speeds of the S ships and find your favorite. Another method is to plan the trade center (starting system) and set your sell distance from there so the ship never enters any illegal space.