Go to a weapons or armor merchant that has two of the same weapon or armor for sale. Purchase the overall most expensive item at the lowest condition. For instance, if he has two Raider Sadist Armors at 35% and 75%, but also has two Flamers at 15% and 7%, then choose the Flamers. Purchase the cheapest of the two items, and then immediately sell it back to the merchant. Purchase it again and sell it back. On the second or third time you sell it and buy it back again, it will appear in you inventory at 100% condition. Sell it back to them, and it will reappear in their inventory at the original low % condition. Buy it again, and it will appear at 100% condition. Repeat this until they run out of money.
In Guardian Peak you will meet an NCR soldier who is wounded. Through some Speech checks, you can get him to give you his gun for escorting him out of the cave. When you get to the entrance of the cave with him, he will speak and you can continuously ask for his rifle, which he will give you along with ammunition. Note: This is best done after earning the perk that allows for over encumbered fast travel.