So, every time a new ban list comes out, after about a week or so, three main deck archetypes are established and used by almost everyone in the competitive realm, with little to no variation. This bothers some people, but it doesn't seem like anything can be done about it, the powerful decks are the powerful decks right?
It is in fact possible to make a deck outside of the competitive realm that can take down top decks, the advantages to this are: You don't have to make a new deck every time a ban list comes out, just make some minor adjustments to yours, people are less likely to have cards side decked that will counter your deck, and most importantly, chicks dig rebels.
Now then, on to the process of making a fun competitive deck, obviously, I can't make a step-by-step process, as everyone has different preferences, but I CAN give some useful pointers.
1. Figure out how you want to win, there are many ways to win, by beat-down, burn, deckout, OTK, EXODIAAA!!!!!(sorry), so figure which way you prefer first, so you know what you're going to build your deck to do.
2. Figure out a second way to win. Sometimes an opponent will have a deck tailor-made to block your win technique, which is why you need at least 1 back-up plan, even if it's the same technique, have a different way to achieve it, (Example: Two different OTK's mixed with a beat-down deck)
3. Monsters. Make sure your monsters work well together, their effects should either focus on helping you win, or helping each other.
4. Spells. Your spells should generally make up for what your monster is lacking. If your monsters have powerful effects, but little attack/defense, you should use spells that boost their stats, or prevent them from being attacked. Contrariwise, if you're running overpowered normal monsters, you'll need cards like dust barrier and swing of memories to help keep them from being destroyed by effects.
5. Trap cards. These are important, most competitive decks nowadays focus on combos, a well timed trap and can break that combo and create an opening. Be sure to cover the range of negation, monster effects, attacks, spells, and traps should all be able to be countered in some way with your deck, and if you're not doing it with monster and spell cards, you'll have to rely on traps to get the job done.
6. This kind of goes with what I said above, be disruptive, if you want to beat a "better" deck, you're going to have to get in their gameplan and interfere with it, side deck cards that are tailored to be against the current competitive decks
7. Search cards. Search cards are useful, because they thin your deck and make it easier to get at your important cards, but don't add to many, lest you get stuck with a handful of search cards with no targets.
8. Trial and error. Your deck may not be fantastic the first time you use it. Every time you duel, win or lose, take note of what worked and what didn't, and adjust your deck accordingly, and you'll see it start to win more and more.
Well, that's all I have to say, take my advice or not, hopefully you learned something.