Strategies rely mostly on using traps to increase ATK in the battle phase and counter, summoning monsters quickly and depending on the situation using desert twister or destructotron to destroy magic/traps.
Most of the fights i lose are either because i failed to predict a mirror wall, a kuriboh gets in the way, or I'm up against territory of the harpies and de-spell doesn't come out quickly
Relinquished is Top Tier, so you can expect to see more of it as you get higher. Possessed Dark Soul at 1 seems to be a popular Tech choice, maybe try a copy? As for GKs, I don't think I know of any Tech choices you could add, Ishzark might be fun though.
Since your deck is essentially a Beatdown deck, you have lots of room for Tech cards, so look at your collection and see what's available...Security Orb is a decent E-Con replacement, a second S/T removal or Bluff trap for those HHG matches, Eliminating the League, Soul Exchange, etc.