This...

Aww, it must have been really tough ㅠㅠ The beginning is always the hardest part! Just hang in there a little longer, Rippli will be cheering you on beside you :D

I haven't played Zombie Waves, but thanks for the great info that the early game is extremely difficult 🤣

I've reached level 84 without spending any money, but I'm stuck at 85. I'm debating whether I should spend money.

After n days from when you start playing, one content unlocks, and after nn days, another one unlocks... That's how it's set up. So you can't unlock many contents early on. ㅠ For now, it's good to consistently collect rewards scattered around, like weapon leveling and equipment synthesis.

If you're stuck at level 139, I recommend not pushing the stage for a bit. Instead, gather materials, gold, or items from other content like the post above, then push the stage once your power level is a bit above the recommended. Also, equip guns that match your character. Each character has different gun types. Is it a shotgun, rocket launcher, rifle, or sniper? Instead of just picking a gun because it looks good and fits you, if you like a certain gun, consider switching characters too. Just matching characters and guns can make a difference even with the same power level.

If it's not a brand new server, you'll have an easier time if you use the gacha tickets you get as a bonus for clearing early stages or the lab after the ranking opens. Save up your diamonds too, right?