Here's how you quickly grab some duel points. This assumes you've started a new game. If you already have one, and some DP, then you'll be farther ahead of the game.
From starting a new game, pick the Fire deck. It has two cards that are perfect for stalling. Then you go and buy packs all the packs of Dark Crisis that you can. When you open them all, after spending all your DP, if you don't get at least one copy of Final Countdown, restart the game, start a new game and pick the Fire deck again.
When you get a copy of Final Countdown, good, you're ready. What you do is go to deck edit and add final count down, then get rid of any card that doesn't help you with your goal. You plan is to get as much money as possible. The biggest bonuses in this game come from having an extremely low amount of cards in your deck when the duel ends, such as being on your last card, doing tons of damage in battle, and having below 100 health at the end of the duel. These are the biggest bonuses I've seen so far.
So what your deck needs to do is to be able to stall. It also needs monsters that "thin" the deck out, by summoning themselves, while also protecting you. So, plenty of cards like UFO turtle.. You also need to live long enough to use final countdown, and you need some cards that let you draw fast enough to get the thing. And finally, you need a backup plan just incase you don't draw your automatic win card. You can still catch some DP for all the time you spent dueling if you have cards like Raging Flame Sprite that, behind a gravity bind, can chip away at the opponents lifepoints and then finish them off, just incase.
I used this strategy, keeping the deck down to 40 cards and using jars of greed to thin it out while playing defense with UFO turtles until I could afford packs of Legend of blueeyes, then I bought the destiny board. My current deck looks like this...
All of the exodia pieces A cat of ill omen Cat's ear tribe Guardian sphinx Hane-Hane TWO Spear Cretins, to create a defensive loop 3 UFO turtles, for deck thinning 1 book of moon Brain Control Dark Hole Final Countdown Heart of clearwater Heavy Storm TWO Level Limit, Area B Mystical Space typhoon Pot of greed Reload All of the destiny board Swords of revealing light the dark door gravity bind THREE jars of greed, but only if your deck has 40 cards, otherwise, it's totally pointless 1 last turn, just incase my opponent beats all of this other stuff, I can take him down with me magic cylinder sakuretsu armor and a wall of revealing light
All of these cards were gotten from packs, except for the destiny board trap card itself, which I bought with the password for like 3900. The most difficult part of getting these cards was getting a copy of swords of revealing light, but even that didn't take too long.
So, there you have it. A deck you can build from the very beginning and then beat everyone with. The only times I've ever lost were when I got entire handfuls of destiny board pieces. To improve this, I'd imagine you'd need more deck thinners or more ways to recycle cards. But before you buy all of these in booster packs, the best way I've found to get final count down is to set a morphing jar number 2 and then flip him so that you self mill your deck, then flip a magician of faith and take final countdown back.