Video update: This playthrough is from April 10, 2015, so this is about as recent an update to the game as you can get.

I finished the game a few times, so I had a massive bankroll I could use to buy everything.

If you're starting fresh, just play through the game a few times to get the hang of it. Try banking as much money as you can.

From there, the first upgrades you want are the discount upgrades from the bank's shop. Then you want life insurance from the bank's shop. All that together costs about 200 gold.

After that it's mostly about exploration and survival. Keep an eye out for hidden walls and bonuses and so on. Try to get every upgrade you can if you can afford it. Use careful backtracking when you can, but without walking through laser barriers (unless you REALLY need to).

My items guide and monster guide have some extra tips about gameplay, so check those out if you want.