Along with Gochujang, I always follow Maangchi's recipe for tteokbokki, which involves both:
for the base broth.
Along with that, obviously would include the rice cakes themselves.
Aside from that, I've never tried mixing a pajeon base mix from scratch, so I'd just as soon buy that as well.
And as far as one of my favorite banchan options, seasoned shredded squid, both the squid itself and rice syrup are both available on Amazon.
That all adds up to less than $100, I think, and along with the gochujang obviously being central to a ton of recipes, the kelp and anchovies can also form the base of budae jjigae along with other soups. The rice syrup can also be a component of a sweet glaze for korean fried chicken. The pajeon mix and anchovies can be frozen virtually indefinitely from my experience, and the rice syrup and kelp are shelf-stable without any refrigeration/freezing. Hope whatever you end up making is delicious!