Stealth: take lily and put on a stealth boy. You can loot Van grafts entire showroom, BoS bunker, and camp mccarran. These alone can be sold back at gun runners for thousands of caps.
Kill: if your a true baddy you can clear out BoS without many repercussions (arm turrets to kill all BoS, bEst done after finishing BoS quests as you can first get trained to wear power armor) it'll take you a couple trips but you can quickly rally a a TON of gear (I use novac as my base as it has room, safe, workbench, and mailbox all close to one another).
Luck: I amped up my luck (you can save some points and buy an implant) then buy the naughty nightwear from mick and ralphs. If you gamble at all the casinos (blackjack is the easiest to pull off) you'll end up with close to 50k (including atomic wrangler and primm).
Caravan: learning the game is a pain, but playing it is very easy. If you build your caravan deck with just 10s, 9,7,6,Jack, king you can easily win each time. Remember to raise your bets to max.
Caravan tip: just try to put down a ten in each caravan and double it with a king. Then u just need a six to win the caravan. I never use queens and occasionally a jack. Really you an just use 10s, kings, and sixes. You'll get caps but you'll often get NCR money and other currency.
I also am trying to get better about selling everything I'm not really using. Pick a weapon type (energy will always be most powerful but sniping or sneak critical attacks are equally powerful due to the high crit. I always finish the game with way too much stuff and money.
I almost wish there were more things to buy or spend money on.
All of this is essentially in the wiki, but I thought I'd put it out there.