So my own experience with Skype and that "****ty", but cheap, cellphone (Wildfire S, by the way, I used the official HTC ROM)... So that's just impossible to handle the calls with Skype. I tried Skype, Skype lite, Skype on 3 (a special version of Skype which allows just the chats, so NO CALLS)...
So I installed Viber. The calls are pretty good even if the sound is quite low... But compare to Skype (desktop software version) that's not the same quality/rapidity!
To sum up : Skype doesn't work well for the calls! Okay you can use it to chat with your friends but some better applications exist (like WhatsApp).