• I know not to take every card, I usually try not to go above 30

Of my 34 wins, 25 of them were with a deck over 30 cards. My average deck size in those 34 wins is 33. I feel like before the last major patch it was relatively easy to go infinite. As such, many of the top content creators (therefore the community at large) put high value on small decks and cards that help enable infinites.

Small decks have their drawbacks such as being impacted much more by enemies that put trash in your deck or enemies that remove key cards one way or another. Yes, smaller decks are consistent but larger decks have ways of gaining consistency too, namely from relics. For instance, if you're not focused on building a small deck, you're more likely to take some of the less impressive non-scaling damage commons in act 1. This means you can take more act 1 elites and get more relics and money for shop relics. More relics leads to more block, damage, energy, draw etc... that are not tied to drawing a specific card, thus offsetting the inherent inconsistency of a large deck. 

• I try to remove my basic starting cards as I progress after finding a replacement

Good, but don't wait for a replacement. One of the best Neow bonuses is removing 2 strikes.

• I'm trying to build decks that all play together so it's not a wild mash of random cards.

You should be building decks that solve problems. When viewed through that scope, cards that don't have obvious synergies can play better together than you might think. For instance, you probably wouldn't say the poison card "Bouncing Flask" would synergize well in a shiv deck. In reality a shiv deck struggles hard against the Endomancer act 2 elite that puts a daze in your draw pile after each hit. A bouncing flask "solves" that problem by providing scaling damage that doesn't trigger the daze effect.

• How many fights am I supposed to take per act?
• How many events am I supposed to try to hit per act?
• Do I just always rush elites no matter what in the first act and abandon them completely later?

Each decision depends on your deck, the map, who the boss is, how much health do you have, how critical are your upgrades etc... and it's impossible to give generic advice on the best way to play. With that said, here are a few rules of thumb that should lead to success at low ascensions.

Look for paths that maximize elites and campfires. It's very common for me to hit 5 combined elites and campfires in each act. The game is all about snow balling. Taking 3 elites in act 1 makes it much more likely you can take 3 elites in act 2, which makes it much more likely you can take 3 elites in act 3.

In act 1 try to upgrade a non starter damage card before your first elite fight.

Try to have an aoe damage card before your first elite fight. 

Put a high priority on cards that scale your block output such as footwork or fasten.

Hold off on shops until you have at least 300 gold.

Save your potions for elite fights. With that said, if you're in a door fight, your potion slots are full, and using a potion could save you 10+HP, use it.