My best advice as far as deck building goes as such, and don't worry I do this for all my decks:
1. Create a theme or focus on a general in/out of game mechanic
2. Choose your creatures
3. Choose your spells to help them survive as long as possible
4. Add and play cards that enhance the theme created by steps 2 and 3
5. Get the appropriate mana ratio down
6. Test the draw simulators on deckstats or play against a friend
7. Make changes as you see fit.
When I build a deck I create it as if I'm building an ARMY. I personally always focus on my creatures because a majority of the time (and also depending on how the deck is built) they are usually the most important part because their own effects can work like spells as well. For example;
korozda gorgon and
howlgeist are two creatures from two different blocks. However if you use the gorgon's effect on the spirit wolf (after it returns from the grave with its UNDYING effect then you'll basically have a spirit creature that won't stay
dead, can become unblockable once the bigger threats are
gone, can be used for sac fodder with cards like
bone splinters vampiric rites, or just an infinite wall as long as you remove the +1/+1 counters from it. This same strategy can be implemented using any creature that has undying and and all you're doing is resetting them without flickering the creature off the board. So basically I just designed a deck idea using just TWO creatures that can be turned into a lethal B/G creature recursion deck. All I would need now are spells to help the general idea expand using other creatures and spells, get the mana right and I've got a new deck. See how that works out? As far as ratio goes just ask yourself: How IMPORTANT is this card to MY DECK? Will the deck fall apart or cease to function if I don't have it in play? If the answer is yes then have 3-4 copies, if the relevance factor weighs lower then add less copies. It's not really as difficult as people think, it's just having the most of what you need as far as what you're going to actually use for the deck. Did any of this help you out at all?