If this is your first, I'd say you're not doing badly. I cannot use Apop., but what I've seen certainly suggests so. The design looks quite promising but it is hard to tell because, yes, it is too dark to tell.
I'm sure some Apop. expert will be along to advise, but I believe altering the gamma would help. At least, it would in Gimp. Increasing the gamma usually increasing the brightness and grain (so there's a balance, usually). Just don't ask me where the control is in Apop.! Also Apop. seems a lot more flexible, so there are likely other options.
You could also use a different gradient, of course, but I'm assuming you wanted this one for a certain effect.
Look forward to seeing later - and, hopefully, lighter and brighter - attempts.
(This is the first you _tried_? Good grief! You're surprised it's too dark? I'm surprised it is _merely_ too dark!)