I used to work at Wizards of the Coast, and got free magic cards all the time, and the online account. After I moved back out to the Midwest, I sold my cards for a little over 2000. Before I started to get out, here are the basic keys to success I was using.
1) Build 2 decks, each comprised of 2 colors. This way, you can change out the nature of your attacks/strategy.
2) 60 cards a deck, try not to go over. The chances of pulling up any strategy are better with fewer cards. The rest of my numbers are based on the 60 deck.
3) Fill your deck with low power cards/creatures first. Then replace a FEW of them with larger ones.
4) Mana count is important. About 22 land does a pretty good job in general for most decks, and then consider if your cards are mana rich or cheap and modify the land count.
5) I recommend about 20x 1~2 cost cards, about 10x3-4, and about 8x5+ cost cards. MTG makes it really tempting to overload your deck with cards of really awesome power, but if you have more of those cards prior to getting the mana out to use them, then you'll most likely take a lot of damage early. Keep a strong practice on not going over the numbers for expensive stuff. I'd be sooner to reduce the %+ cost cards than increase them.
6) STRATEGY!!!! to do well, you really need a solid strategy. Typically a singly deck will have 2 colors, and with that 2 focused strategies that 80% of the cards support (mana excluded typically) You also need defenses against a variety of strategies.
- Example, Having a pair of artifacts to prevent flying, and atleast a pair of instants to cancel an artifact destruction card. Or you need cards for flying defense.
- Example, Increasing your mana, and having artifacts that allow mana to be spent directly/repetatively on attacks or defenses.
- Reducing your mana, and 5+ cost cards, while increaseing the 1-2 cost cards, giving more upfront effect in the game, I.e. your deck could focus on early damage, in a game, and cheap defenses.
- You could focus on summoning, and then most of your cards should enable, enhance or protect this abilitiy.
- Ideally, you would watch games in action, and see strategies. Get MTG online and watch games in play from high ranked players. Look for strategies that appear to work.
7) Keep your expensive cards low. I know I said this already, but I can't (I'm sure I actually can) express this enough. Unless you have a rock solid Mana delivery system in play, focusing on the creative and powerful will usually leave you too vulnerable at the beginning.
8) Strategy Count should be low. As I said before, you'll want 2 for offence and 3+ for defense. If you go over these numbers, chances are you'll not pull cards that support each other in your hand, and the cards will have far less impact. Imagine that every card that matches the same strategy as not having a cumulative effect, but a multiplying. 1 card to summon, vs 1 card to summon and one card to enhance that are significantly different.
my best deck had 6 cards costing more than 6, and 25 cards costing between 1 and 3.
My favorite deck was all white, with only 12 mana, and all the cards cost 2 or less. Only won about a third the time, but put up an amazing fight, thwarting nearly every action from these powerful decks. Repetatively shutting down their amazing efforts with incredibly low powered cards. Eventually I added 2 of the Angel cards, I can't recall the name, but I believe it cost 7 white, and when cast, you could pick one color, and no spells of that color could be cast.
Any way, good luck.