Ok, so
1. Getting strong is really easy if you don't care how you do it, spamming potions can make you really strong for singular encounters, growth multiplier potions are especially powerful. Also make sure that you take all the buffs that you can at town like the mystery fruit, slime buff merchant dude, and exercise or drinking.
2. Leveling is a bit of a grind but a couple ways you can make it better are with xp multiplier gear like the weighted armors, broken sword, and xp and ego multipliers in the total side of the skill tiers and/or if you want to get a bit more dangerous you can buff enemies in combat with intensify which will increase the xp they give. the commander enemy is particularly lucrative if you keep the fans buffing each other and not the commander both because there are a lot and because they end up giving huge stat buffs, just make sure to kill them before it gets too out of hand.
3. Finally, take a look at your gear. Some weapons are really good, some are really not, some seem good at first but fall off hard, and a few are only good in certain synergies. You can take a look at your weapons' damage in your stat screen. Also make sure to properly allocate stats and essences for your build, you can reset essences at the green dude in town and stats at the plush before the final area.
edit: almost forgot, but npc allies can also make your life easier and I highly recommend setting your size growth multiplier to max for increased range.