What does it mean by level?

As far as I can tell, the closest thing to a player level is the level you have for any specific hero. If that's the case, that's a problem. When starting as a new account, you only have access to free trials as characters. I reached level 7 with one of these free trials, but I won't be able to reach level 8 until I manage to get enough soulstones to summon them, or get lucky with the next randomized free trials. This wouldn't be so bad if reaching level 8 was reasonably quick, but it isn't. From level 1 to 5, it took me an hour. From 5 to 7 it took around six.

Alternatively, they mean battle pass level. If that's the case, problems solved- I just want to know what it is I'm supposed to be aiming for.