Hiragana help needed

[benevolence dragon]

Please help me, I dont understand how it works. My sensei gave me a chart that is supposed to help but i dont understand it. their are all the usual ones like a,i,u,e,o and ka,ki,ku,ke,ko but then their are also those hiragana that when you put a circle or those two lines over the usual hiragana it canges the sounds to ga and so on. sorry if this doesnt make any sense but what i need is help understanding what those signs above the usual hiragana mean and a way to memorize their meanings or a new chart all together  

[Teddiblue]

I found that using flashcards was the most helpful way of me learning.

Its the same way when you learn the basic Hiragana, it goes Ka sa ta na ect.. and then when you add the two lines over it, it changes to Ga Za Da Ba.. ect.

I also find it useful instead of learning the basic Hiragana first, and then the extra, Learn them all together.. like study Ka and Ga.

But make flashcards (it also helps you learn out to write them) and it will help you alot!

 

[=X-Sparker + AquaKiller=]

Here is a more comprehensive hiragana chart (Ignore the Katakana on the right if you're not learning it yet):

Basically, the two diagonal lines does the following:
k --> g
s --> z/j
t --> d
h --> b

The little circle does the following:
h --> p

They really are just an indication of a slight change in the pronunciation of the consonant of that hiragana.