Welcome to the forum and MTG! I am also a budget player (college is expensive) so I can sympathize with you there. I was ecstatic to pull
Liliana, the Last Hope in the Eldritch Moon sealed event I played at. I also like to play aggro or tribal decks (both if I can get it) and my current favorite is my B/R vampire tribal so I'll offer you some advice! I'll apologize now for a long post.
One thing you need to keep in mind when building a deck is strategy. How are you going to win? Are you going to play aggressively (more offensively focused) and
overwhelm your opponent with a horde of cheap creatures? Are you going to play control (more defensively focused) and counter every move your opponent makes? Or are you going to play Mid-range and adapt to whatever situation you find yourself in? Your deck right now doesn't have a clear plan for winning. You have some life drain/gain, some counters and madness, and graveyard recursion, but there is no big combo or creature strategy for sealing the deal on your victory.
Also consider your synergy. Synergy is what happens when all of your cards work well together. Your creature types are all zombies and vampires yes, but do they work well together? You want cards that have abilities and spells that help each other out. Like playing
Macabre Waltz with
Alms of the Vein; they help each other out because you can discard
Alms when you play the Waltz and then play
Alms for one mana at it's madness cost. You want to play cards that work well together. Another example is your
Gavony Unhallowed with a card like
Nantuko Husk;
Nantuko Husk would let you sacrifice a creature at will which in turn would put a counter on
Gavony Unhallowed as you need to instead of waiting for your opponent to kill your creatures.
You could try playing more than one color. Most starter decks are two colored. This is so that you can play cards that work well together and have the advantages of more than one color. Black, as you've noticed, is great for graveyard/sacrifice perks but blue, for example, offers some more control and draw card options. U/B zombie tribal decks can be a lot of fun. Since you are playing with cards you own this also gives you the option of having more cards to choose from rather than limiting yourself to cards from one color.
Lastly, I tend to order cards online when I can't get to the shop to buy them. Opening packs is exciting, but you will save money if you build a deck on a site like this and then buy the specific cards you need.
I hope that helps you a little bit on your deck building journey! It's great that you are building your own decks from scratch. This site is a great place to ask people for help.