to get weapons, simply buy them from agws shops. the weapons that are unequipped by the agws become available in the minigame. basically, take all weapons off the agws, then enter the minigame to have access to the ones you have.
to get the agws suits in the game, you must have them for your party in the story. to get the last 3, you need to buy the secret agws units for characters. you can buy them from the dock colony agws shop near the end of the game. there are the vx-4000, the ag-04, and the ag-05.
they are expensive, so i suggest you get money from the 4 soldiers and the 1 mech ship in the encephalon sim. ((the enemies on the map that have the spotlights)) - as they give you the most money in the game. about 1600G.