Well, if there's nothing to buy, I jsut level up with the Souls. *shrug* I'm pretty sure i've wasted upwards 30k Souls allready as well, but just like in DS1, it's not a limited ressource.
Even IF you manage to kill absolutely everything in every level you go to, and hit a point where you're stuck (Sentinels, Iron Keep, Gutter), there are bonfire effigies. And even after that, you can allways put your White Soapstone down and help someone with a Boss, which spawns you as a human afterwards, gives a ton of souls depending on the Boss and also gives other cool rewards, depending on the Covenant. Apart from that, there's also PvP of course.
I also want to point out, Shields DO feel like they're really really op sometimes. I'm playing a Swordsman, and my only Defense is dodging. Against Bosses like the Smelter Demon, or stuff like the Sentinels, this means that usually even one hit will be your undoing, depending on how trigger-happy the Boss/es are after they've hit you, and you pull your Estus.
You will probably laugh, but playing this Character has actually RUINED shields for me.
On my twink, I got so annoyed that I did so little Damage, that I started Dual Wielding my Big Weapon right away. I cleared Heide and the Forest with exactly one death (The summoned Dude at the Pursuer shot me by accident, Ballistas do hurt.). The only time I really used the shield was against the mace-wielding Giant, because I still cant get that guys pattern down right. This isnt meant to boast, I just want to emphasize how much you as a player improve, and how much easier the game gets with that. Dead Man's WHarf still kicked my ass tough, quite a few times.