I read on this very subreddit that farming the Herbalist will let you level up Haven Island which in turn will reward the Sieker at lvl 10. The Sieker is one of my favorite items in Freelancer so I decided to go throgh with this. This is for the part after you've done all the challenges so if you haven't, do that instead. Number of runs needed will depend on how much XP you got during the various challenges, but for me it was about 7-10 runs of just farming afterwards. At about 2 minutes per run, not counting loading screens, scoring screens, etc., it took less than an hour in total after having completed all challenges.
Not guaranteeing my way is the most xp/min, but it's pretty fast, pretty reliable, and doesn't require very much skill so you can focus on a podcast or whatever while you grind a little. I did die sometimes but it's quick enough that it's not much time lost.
My way of doing it was as follows:
- Start at the villa terrace. This puts you right next to Cyrus when you start. Bring a lockpick and your favorite explosive, in my case that would be Napoleon Blownapart.
- Run over to Cyrus and drop the explosive.
- Move in towards the stair on your right. When you get into the house, blow up the bomb, killing the main target and a bodyguard or two (extra xp :) ),
- Run up the Westmost stairs. Depending a bit on the exact timing of the bomb, the guy atop the stair might be looking out towards the balcony or he might look straight at you. If it's the latter, shoot him in the head. If not, it's usually not worth the extra disruption for 5 xp so just run past him.
-Turn left, lockpick the door to get into the room with one staff. Pop his head, steal his fit, and grab the dongle from the safe on your left. Don't forget to pick up the speedboat key on the far side of the bed for 10 xp.
-Go down the closest stair and to your right into the security room. Ideally there's just the two guys there loudly discussing the location of the dongle you should already have. Sometimes they would run out to check on fatalities, sometimes civvies would run here in panic.
- Close the door and headpop everyone inside before they can fire back at you. Start with bodyguard (in the suit) and it should be fine, event security guy doesn't notice so you can easily pop him as well. That is two disguises you can put on for 50 xp. Shoot the camera thingy for another 50, use the laptop to finish the main objective, grab the villa key for the xp, and leave through the glass double doors dressed as a guard.
- With a little bit of luck you can now simply stroll away. Don't stop to fight unless you have to. Turn left outside the doors, move straight forwards, and jump the fence into the flower-balcony. Move a little to your left and jump down. Run towards the nearest exit, the seaplane, and excellent work, 47.