Budget decks

hey! I would like to return to the hobby after a long time, but on a budget scale - I want to play with my family.

I used to build meta decks, but I definitely don't have time to go to tournaments anymore.

What is the current price of building a deck that works - is fully playable - and I don't mean theme decks that have 20 energy and a lot of useless pokemon and trainers.

how does it look now? do the Ex Battel Deck available in stores have any good cards? can they be improved to just be playable?

What are actually must have trainers cards which are in every deck ?