A1
: 
Cheating duel points, without a hacked save game, it's impossible. But here's the easier method I've found:
There is a Slifer Red Duelist named Moses. He runs a Fairy-type deck. He has 2 of them so far, Heroine Battle 1 and Heroine Battle 2. If you unlock him in free duel, you can duel him, as his Heroine Battle 1 deck doesn't use very powerful cards. (The most powerful is a Marie the Fallen One) His Heroine Battle 2 deck uses some of the most frustrating and powerful cards around, but by keeping Gellenduo and The Sanctuary in the Sky off the board, it's possible to keep it reasonable. Of course, I have a deck I built. (Spent a lot of time playing to unlock the packs and get the DP to make this deck)
Heroine Battle 1 gives you an average of about 600-700 DP a win, depending on the bonuses.
Heroine Battle 2 gives you an average of 900-1400+, depending on how long the battle takes, and what you accomplish. That being said, here is the deck I made.
Airknight Parshath x2
Archlord Zerato x3
Cestus of Dagla x3
Chain Burst x1 (Stops his Draining Shield and Enchanted Javelin cards)
Dark Temple's Bribe x3
Draining Shield x2
Gellenduo x3
Guardian Angel Joan x3
Heavy Storm x1
Mage Power x1
Marshmallon x1
Mystical Space Typhoon x1
Neo-Parshath, The Sky Paladin x2
Nova Summoner x2
Snatch Steal x1
Swords of Revealing Light x1
The Sanctuary in the Sky x3
United We Stand x1
Warrior of Zera x3
Zeradias, Herald of Heaven x3
Zolga x2
The purpose of this deck is to out-power Moses. Here is how I normally do it.
Gellenduo counts as 2 Tributes if you Tribute Summon a Light Fairy-type monster. That will help you put out Guardian Angel Joan (8 star) and Neo-Parshath, the Sky Paladin (8 star). I normally put 1-3 Cestus of Dagla on Neo-Parshath, so when he deals damage, I gain 1-3x the damage he deals in life. With a "The Sanctuary in the Sky" on the field, Gellenduo and Marshmallon are invaluable, because none of his monsters can deal piercing damage. (Damage that is dealt equal to the difference between the ATK of the monster, and the DEF of the target)
Guardian Angel Joan should mainly be used to attack his monsters, so you can gain life from destroying them. Archlord Zerato (Special Summoned by Tributing 1 Warrior of Zera while The Sanctuary in the Sky is on the field), helps by eliminating monsters you just don't want to deal with. If you control The Sanctuary in the Sky, and discard a LIGHT attribute monster, you can destroy all of your opponent's creatures.
Dark Temple Bribe cards are in there to stop the more annoying traps/spells, or if you REALLY want to get your damage in, to gain the life.
If you drag it out near the end, having been attacking and gaining life, you can net about 1400-odd DP per battle.
The other way is to find a duelist that you can defeat easily with your deck, and continuously beat on them, until you have the DP to purchase the cards. Most of the cards I listed above can be found in the "Celestial Sign" pack, unlocked by either beating the game with 5 Tier 1 characters, or winning the Slifer Red Tournament.
Trust me, I looked, but it is REALLY hard to cheat DP in this game, but these are the most effective ways I have found.
A2
: 
The ansver up is good,reali good,but set the life points on 2000,and make a deck full of cards like okkazi and final flame to beet your opponent in 1 turn.