Well i sorta know how you feel on having so many good ideas and not being able to use them all in time.
I myself have that problem which is why I have my set files the way they are...
I have a "test" set where every new card i create starts it gets tweaked noted with version #s and I keep any flavor, theme, and story idea in the card notes box.
I then have a "Finished card" set where all cards go when I have stopped working with them. From this set i have to opportunity to then take any combination of the finished cards and throw them in a set file.
Should a set need specific cards later down the road I start making them in the test set.
The system I run works really well for me and even lets me keep track of which cards i have put into which sets.
Creature - Elephant Assassin (R)
WU: ~ gains flying until end of turn.
RR: When ~ loses flying ~ deals damage equal to it's power to target creature.
4/4
Next: Dragon ---------- Drone
Roaming Murkwater BB
Creature - Elemental (C)
When ~ enters the battlefield you lose X life, where X is the number of players.
When ~ goes to a graveyard from play search your library for X basic lands and put them into play tapped divided evenly among the players. Shuffle your library.
3/1
Next Suggestion: Any from page 11
Land - (U)
~ enters the battlefield tapped.
~ doesn't untap during your untap step.
T: Add WWW to your mana pool.
Put 2 1/1 white spirit tokens with flying onto the battlefield under an opponents control: untap ~.
Next suggestion: GGGGGG
Creature - Elf Bebble Druid
~ is unblockable as long as defending player controls a non-land non-creature permanent.
T: Add G to your mana pool.
2/2
Next: Dragon ---------------- Merfolk
As for Ninjustu um.... yeah I got nothin.
Legendary Creature - Beeble Nephilim
As long as Defending player controls a multicolored permanent, ~ is unblockable.
Whenever an opponent cast a multicolored spell you may draw a card.
5/5
Next: Kor -------------------- Kraken
Creature - Homarid Ninja
At the beginning of your upkeep sacrifice a creature or put the top two cards of your library into your graveyard.
Ninjustu BBBUUU
BU: ~ Gains shroud and becomes unblockabe until the beginning of your next upkeep.
Next: Ferret ----------- Knight
Creature human Horror
Intimidate, Wither
Other black humans get +3/+1
Non-Black humans get -3/-1
"His fellow corrupt walk in darkness, All others run in fear."
Next: Wall -------------- Nomad
Tribal Sorcery - Dragon (R)
Put 2 2/2 red dragon creature tokens with flying onto the battlefield.
Mulitikicker 1
Put a 2/2 red dragon creature tokens with flying onto the battlefield for each time ~ was kicked.
Cycle suggestion: 0 Or a land
Creature - Fish Zombie Mutant
Upkeep BUG
When ~ would go into a graveyard from the battlefield return it to your hand instead, then shuffle your graveyard into your library.
9/9
Next: Ooze -------- Ninja
Creature - Ooze Wizard (C)
If you control another black creature ~ gains Intimidate.
If you control another green creature ~ gains Reach.
If you control another blue creature ~ gains shroud.
2/2
Cycle suggestion: 7GU
Sorcery
Each player chooses a permanent on the battlefield that he or she doesn't control.
Exile all permanent chosen this way.
Next: 2RR
Creature - Rabit Ooze
Whenever ~ is dealt damage put a creature that's a copy of it into play.
1/1
Next:
Eldrazi ----------------------- Goblin
Creature - Bear Knight (R)
Trample, Flanking, Vigilance
3/3
Cycle Suggestion: 2GBU
Legendary Creature - Merfolk Wizard Cleric (M)
When ~ enters the battlefield search your library for two white permanents two blue permanents and two black permanents, put those cards onto the battlefield. Shuffle your library.
4/4
Next: 2GGUUBW