I suck at building decks in this game, any advice?

Any time i try to build a deck from scratch, disregarding the meta and working only with my collection and what i think will synergize or be fun, the deck actively sucks. Consistently losing in ladders, with my combos being cut short and sometimes predicted perfectly.

This normally wouldn't be a problem, but because of gwents slow, methodical and tactical gameplay, it really disappoints me that i can't seem to build something that works without looking at netdecks.

Let's take saskia and Milva for example. ST is my favorite faction, so when i came back to the game a few weeks ago i bought these cards immediately and tried to make 2 decks, one with Sask and one with Milva.

The saskia deck was utter crap (though i probably played it wrong) and i messed up playing the milva deck the first few times. Then i realised she was stupid broken and wasn't conducive to clever deck building or game play anyway.

Now, i still have those 2 decks (One is devotion torque handbuff with sask, the other guerilla tactics move engines with milva) but i pretty much don't even want to play the game because i feel like i need my hand held.

I opened some PoP packs yesterday and got very lucky; picked up 2 or 3 NG golds (Cahir, Rience and possibly a purple i forget) and tried to build a deck with them, but my terrible building skills are always compounded worse when trying to build for NGs complicated gameplan, even with fresh top tier cards.

The only decks I've ever built totally alone that worked well are skellige decks. Skellige being the easiest faction to build anything with due to how simple their archetypes are.

I just lost a match against a GT movement engine deck when i was using devotion handbuff saskia. That fuckin hurt, because i literally lost to my favourite deck style, using a VERY similar decklist to mine plus some less than perfect meta cards like Gaetan, amd it STILL thrashed me without using milva or Saskia.

So tldr; how can i improve my deck building? I'm sick of being forced to netdeck and then sucking anyway.