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Sell your Silver, and start the mission. You might as well pick up some H-Fuel to sell at Willard. Launch and fly the first part of the mission.

When you get to Willard, sell the H-Fuel, buy a new shield and continue back to California Minor. Load up on H-Fuel again, and it's back to Willard.

[edit] Interlude

When you land you'll be at Level 6, so you can buy Class 4 weapons/shields and Razor mines, though you can't find a Class 4 shield in Liberty. Go ahead and explore the California and Texas systems now. After you start Mission 4, you won't be coming back to Liberty for a long time. There's a Junker base in NW Texas and a Rogue base in E California; you can use the Patrol Path map to find them.

If you are so inclined, now might be a good time to try your hand at piracy. You probably want to confine yourself to preying on the Liberty corporations: Interspace, DSE, Ageira, Universal and Synth Foods, since they like you a lot and will hate you as of Mission 4. Just shoot a trade lane out in the middle of nowhere until it breaks and then blow up transports that come by. Apparently with trains and heavy transports, you can just shoot off the cargo tanks instead. It'd take a lot of piracy to make them hate you.

Another approach to piracy is looting Storage Depots. The middle one near Manhattan contains Polymers, which sell for $491 on Denver. One of the depots near Fort Bush has H-Fuel, which sells for $360 on Manhattan. Note that if you leave the system and come back, the locals will forgive you.

If you just want to trade, running Beryllium from LA to Pueblo Station makes $180 each. On the reverse trip, Superconductors earn $79.

Before you hook up with Juni again, pick up some Engine Components at Houston. You can make $824 each selling them during the next mission.

By this point, you may have annoyed enough other people that the Xenos feel positively towards you (i.e. the bar goes to the right). If so, you could visit Ouray base and buy some of their excellent guns.