大家好

你们好，我叫Garrison。我会说一点普通话。我说的不好。:)

1. 我会说一点儿普通话，但说得不好。

2. 我说的不好。 the structure of this sentence is :S(我说的=what I say/said)+V(不好） It is just like your are saying "Sth. is bad." 

    我说得不好。 the structure of this sentence is: S(我）+V（说）+Adv.(得）+Adv.(不好）  It means : I don't speak it very well.

大家好

你们好，我叫Garrison。我会说一点普通话。我说的得不好。:)
 
Red is fault, green is correct.

It's just like, speak good and speak well. 

Speak good 說的 好 ;   的 is an end of Adjectives. 
Speak well   說得 好     得 is an end of Adverbs.

and if you can add a  conjunction ' but, ' that will make your sentence better 
我会说一点普通话。但/但是我说得不好


Garrison, I can't tell that you speak Chinese well or not. But there's no big problem with your writing :D. If you need some one to talk, let me know. I also want to learn English through Speaking English ! if you can do me a favor, that's awesome !!! 

大家好，我叫Garrison，我会说一点普通话，但是我说得不是很好。:)