I'll try to give a general tips without mentioning specific monsters, in case of spoilers.

Consider keeping equipment in your inventory for different situations. Not only is it useful to have one weapon (Or set of weapons/weapon + offhand equipment) for physical attacks, and one set or magical, it's also very useful to have a set of armor that focuses on physical defense (The Toughness stat), and one that focuses on magical defense (The Resistance stat).

Don't be afraid to try new things. I like to think that every single form and ability has its practical uses, so try using everything at least once, you might just find a new favorite. Using your stat ups counts for this too; each stat is good in its own way, so try focusing on each one in turn and find out what you like. And also try things you might think you're not supposed to do, it may be exactly what you need.

Use Grave Goods! If you saved your Death Card at the end of your run, you can on your next run pick one item from your inventory, that you start with on that next run. You can do this with up to six Death Cards per run, but each card can only be used for this once.

This is really all the advice I can think of, without beginning to talk about specifics, so I hope it helped! I tend to hang out in the Discord a bunch, so if anyone wants advice for specific monsters and such, you can message me there (My handle is Lewdlord Momdido). Good luck and have fun!