First-time Player: Help with Understanding/Optimizing Build

[Mescalinic]

Taking setting-exclusive classes with setting-exclusive feats that require access to setting-exclusive rules is very not cool. Shadow Adept's feats require a bunch of stuff that's related to the Weave and Shadow Weave, which are FR-only concepts. If your DM is not using FR, you'll just be giving him an unnecessary headache.

I am in a Forgotten Realms 'table' and my character (a nihilistic criminal, amoral but not particoularly "evulz") is a Shar worshipper... that's why I said that now that I've read about Beguiler and Shadow Adept, I found the class perfect and interesting

Also, remember: when optimizing for actual play, you can't make your character too hard to counter, otherwise your DM kills it off, and those feats are very imbalanced in general since you're trading a minor weakness for a 50%+ defense against counterspell and dispell.

oh, that's interesting... I really know nothing about that, so it's not easy to me to understand the difference between what is 'good' and 'make sense' (which is what I'm looking for) and what is overpowered/uncounterable (which is NOT what I'm looking for)

But I'm not sure I understood the last part... when you talk about "imbalanced" are you talking about Shadow Adept itself?
As in, the fact that a Beguiler get 1 level of Shadow Adept is enough to make the build broken and overpowered?
Or is it Shadow Adept itself that is just broken, no matter what class you come from?

EDIT: to be clear, this table has very clear limitations (for example, sadly I've just read that I probably can't have Shadow Conjuration... that sounded super cool because of those 'utility spells', useless in combat but funny for roleplaying) and limited manuals... so I thought that everything that's allowed, is supposed to be "okay" :)