So my jam idea is to create conversions so you can fill out your deck with a bunch of random cards you have on hand. Or invite that friend of yours who has 30000 unused magic cards to play and they can just grab a few of the ones with the best art. Or if you happen to have the complete set of Who Framed Roger Rabbit? movie trading card maybe you can use those. But also I like to try different odd things in design so my process, if it is acceptable to the mods, will be to write it here in this thread so people can comment or suggest or whatever. This Most likely will result in a simple looking pdf with no frills because I don't really have a graphic design brain. But that's my plan.

Basiic TCG MTG rules v.0005 the basics

A card's level is it's converted mana cost. Total up how many colored mana symbols and uncolored mana it would take to cast in MTG. That's the card's level. You do not need to generate specific kind of mana for basic tcg mtg cards. A basic land has a level of 1 but can only be played as your 1 free level 1 card on your turn.

Otherwise the card functions like a normal Basic TCG card.

Damage works as usual for Basic TCG, impacting level.

When deciding if a non MTG card counts as a certain type of card, decide it amongst yourselves filling in the blanks as you go and always be having fun.

Is a duck a creature? Probably. Is an egg? Maybe. 

Is an oven also an enchantment? It would be funny if it was so yes? 

Generating Mana: If a card generates mana, it instead generates an equivalent number of levels that you can use for playing cards. They do not need to be sacrificed unless that is part of the ability.

Tapping: If something would cause a card to tap, it is an action that uses up that card action. If something would not cause a card to tap, it is a passive that should be considered in effect. If a card has an ability that doesn't cause it to tap but does seem like an action, using the  action allows the card do the action several times in a row at once but then that's its action for the turn. If this card can take other actions as well you can use those other actions  but if any of them require tapping, then the action is gone.

If an action requires mana, you can also generate mana by sacrificing cards in play or discarding cards. A sacrificed card in play is worth a number of mana equal to its level. A discarded card from your hand is worth one mana. All mana is colorless so don't worry about that.

Example: 
Llanowar elves can be tapped to generate one green mana. That means as an action Llanowar elves can let you play a level 1 card or contribute 1 level to a larger card. 

Sensei's Divining Top lets you spend mana to look at the top three cards of your deck and put them back in any order. You can do that as many times as you want in a row as an action since this doesn't require tapping. But there isn't much point to it. And you have to spend mana each time you do it.

Basic TCG Magic the Gathering Rules: v.004 Creatures 

This is a scenario that doesn't change the rules or endgame of Basic TCG. It simply enables the use of Mtg cards as part of Basic TCG decks. 

A card's level is it's mana cost (total up the number of mana symbols and the number of colorless mana a card would require to cast, that is its level)

Optional Combat Rules if you want to be able to make creatures fight: 

A creature's power and stamina are independent from its level. So if you have a level 2 creature with  3 power and 3 stamina, an action dealing 2 damage would remove it from play but it would need to face a power 3 or level 3 creature in combat to be removed from play.

If a card has a +1/+1 token on it, that affects it's power, stamina, and level. So if a level 2 creature with a +1/+1 token takes 2 damage, it would still be in play a long as it has that token.

If a temporary effect such as a spell or instant give a bonus to stamina, that gives a bonus to level as well only for the purpose of determining if the card is removed from play when taking damage. The card can be removed by taking additional damage or by the end of the effect giving it the bonus.

Any creature card has the following action: Attack: Choose a creature controlled by another player. If the creature's stamina (or level if it does not have stamina) is less than this creature's power, it goes to the discard pile. (The goal here is to give creatures ability to attack like in MTG). If that card's power (or level if it doesn't have power) is equal to or higher than this creature's stamina, send this card to the discard pile.

Any creature card has the following passive: (Blockable): When this creature uses it's attack action, the player whose card is being attacked may block the attack with a different creature if able. They then compare power and stamina (or level) as normal. 

Most abilities should be used as written remembering to fill int he blanks as you go.

Some common abilities:  (First strike): If the attacking creature can send the attacked creature to the discard pile, do not check to see if the attacking creature also gets sent to the discard pile unless both have first strike. 

(Flying): If the attacking creature can fly, it can only be blocked by flying creatures and creatures that can block flying creature. 

(xxxxwalk): If the attacking creature has the ability to walk, if the defending player controls terrain or a card containing terrain of the specified type, the creature may not be blocked. 

(Poison): When attacking, the creature also deals damage to the creature it attacks. 

(Deathtouch): If the creature attacks a creature, that creature is sacrificed at the end of combat

(Defender): The creature cannot attack

(Protection): The creature cannot take damage from, be discarded by, or be target by the color of card it is protected from. (Protection from white suddenly got a lot more powerful?)

(Reach): The creature can block flying creatures

(Regeneration): You may discard a card from your hand to prevent the creature from being discarded from play

Basic TCG MTG card v.0001 sorceries

All of these cards have:
(Passive): After doing their written effect, they are sacrificed.

Basic TCG MTG card v.0001 enchantments

They basically function just like normal Basic TCG cards.
Cards that enchant a specific thing need to be attached to another card of the type they enchant.

Basic MTG card v.0001 instants

These cards have the following passive: 
(instant): may be played at any time in between or in response to another player's actions, including not on your turn. You must be able to sacrifice cards in play to pay for this card or have mana sources in play to pay for the card.

Basic TCG MTG card v.0001 artifacts

Unless otherwise stated these cards are colorless. 

They are not creatures unless specifically stated to be so. 

Otherwise they function like normal basic tcg cards.