http://www.brusheezy.com/
http://www.dafont.com/
Brusheezy for more brushes, dafont for more fonts. No registration required and all free. You just have to know what kind of brushes and fonts you're looking for, and for that, just keep in mind what kind of theme you want to have going on in your signature.
I personally don't feel that I'm qualified for judging other's sigs myself, since I don't consider myself skilled either, but...
As far as text placement goes, I personally find it one of the most annoying things to do at the moment. It's really hard to place text on a sig without it feeling out of place in some way, yet you really want to try and have your text stand out in some way that's appealing with the rest of your signature. You also may want to look into using different brushes or C4Ds to add in some effects to the empty space you have in sigs. Bigger signatures are always great for showing off more of your render, but you have to do something about the extra space you have.
First signature feels out of place in a way in my opinion. I don't know much about touhou, so I don't really know whether or not those ufos are supposed to be related to her character (I'm going to assume they are though, since I remember hearing something about ufos with touhou or something). Next, look at the direction of the rain falling down in contrast to how her skirt flows. The dress should be flowing the other way around along with the direction of the rain falling, and in the end it slightly interferes with the flow.
The second signature, I think a different background would have worked better. Not only that, but with this sig and the previous sig, I feel that the girl is just being placed over a background, not entirely fitting in with it. Though considering how you stated that you lack brushes / C4Ds (I'm assuming that's what you mean by effects) and fonts to use with all the extra space you're leaving open, that if you try getting your hands on some and learning to use them, you could make yourself a good sig.