I'm not sure I've ever asked: do you have any general tips for getting far in Binding of Isaac? I've picked it up on and off over the last few years; I have only one victory and a streak of ~-300 at this point. I basically know to just not get hit, and only just realized the slot machine in the stores keeps its count between attempts, and there are rewards (of which I'm unaware) for feeding it.
Yup, the machine in the shops is a donation machine, and there are unlocks tied to getting to certain donation milestones. You can also bomb it, and it will drop a small amount of coins.
There is a ton of meta stuff involved in this game, and I could write a book on all the advice I could give. The best players out there know all the little ins and outs of the game, and more importantly, what items help/hurt your build, which changes per run. Your best resource for items is platinumgod.co.uk, which has pictures of each item and a description of what each does. Don't be afraid to turn items down if they're not helpful. I know when I started out I took everything, which often leads to disaster.
This might seem odd, but play on hard instead of normal. It is a bit harder, sure, but you get way more unlocks through this mode.
As far as your build goes in each run, in general damage and tears are your best fried. You can turn on stats in the options, which will show all your stats along the left side.
If you haven't figured out the Devil/Angel deal mechanic, basically you have a percentage change starting on floor 2 to get one of these rooms to show up after the boss fight. It starts at 100% for a Devil room at floor 2, but taking red heart damage drops that chance, and it can drop twice if you take damage in a non boss room and a boss room. Black and blue hearts are your best friend here, as you can take damage without losing your chance. Starting on floor 3, you can get an Angel room instead if you don't take anything in the Devil room. The chance is higher if you ignore the Devil room completely. If you're playing Repentance, getting the Angel rooms seems to be the better option overall, health is just too hard to come by now. Pre-Repentance, Devil was the better option. Both rooms have some of the best items in the game, so they're almost essential to getting a strong build.
Another simple rule I follow is to go for item rooms over shops.
Just some more advice, memorize enemy patterns. Special colored enemies do a full heart of damage instead of a half, so avoid those above the normal enemies. Also, look for rocks that are slightly off color and have an X on them. They're called tinted rocks and tend to drop the blue hearts or other items, and can also drop an item called the Small Rock, which is a damage up but slight speed down. Almost always worth taking if it shows.
I could go on and on, but is there any aspect of the game you seem to be struggling with most?
Honestly, the game gets a little easier as you play and unlock more items, but it is challenging. Some of the best stuff has to be earned first. I started a new save file recently and often struggle due to lack of getting overpowered. And if it's any consolation, I have 1300+ hours in the game and spend more time in a loss streak than a win streak.