IF you like waterfalls visit reverstan. The Corbet's gap area does not have many waterfalls even though there are plenty of streams there. Also I don't think that visitng both Reverstan and Deanston (corbet's gap) in a three day trip is a good idea. It is possible but will be too tiring. Its better to focus on Reverstan and later plan a separate trip to Denaston.
Assuming that you plan to stay at Illukkumbura let me suggest the below plan
Day 1: Reach Illukkumbura via Kanday/Matale. On you way at reverstan you can climb the reverstan peak. Its a 1.2 KM easy walk along a well paved raod leading up to the telecom transmission station.
Passing reverstan, on you way to Illukkumbura you can visit mini-world's end. Plan to be there around 3.00p.m. If the weather is clear, you will be able to see the beauty of Pitawal plains in evening light. Miniworld's end trail is also an easy walk of 1.5KM
Reach Illukkumbura forest camp for night
Day 2: Visit Sera-Ella (its about 10km drive from Illukkumbura) will take half a day. The in the afternoon you can visit Rathninda Ella and Wedda-Peni Ella. To reach them you have to drive towards Reverstan from Illukkumbura and then take the route to Pitawala, Rathninda. The road goes passing Rathninda Village where Rathninda falls is located and Wedda-Peni ella is located at the boarder of Rathninda and Etanwala(the last village on this side of Knuckles). You will have to talk the last bit (about 500m) to reach the waterfall.
This will prettey much take all of you day 2.
I haven't visited bambarakiri Ella but I think it is close to Illukkumbura so you can do that on day three. Also make sure that you spend some time cooling off in the Thelgamu - Oya which boarders the forest dormitory
Dhuwili Ella is some what unreachable unless you are ready for a hard hike up to a fair height of Knuckles. It will take a full day and will be quite difficult. You have to walk from the etanwala village, through the mountains on the foot path to Kalupahana to reach Dhuwili Ella.
This trail guide will give you an idea of the routes that cover Rathninda, Wedda-Peni Ella and Dhuwili Ella - http://www.lakdasun.com/trails/maningala-nature-trail-from-etanwala-to-illukkumbura-knuckles-range.htm
I haven't heard of "Bambarun gahana Ella"
Oh.. I forgot .. check this trip report i posted about my visit to this area few months back - Reverstan, Pitawala Pathana, Maningala, Thelgamu-Oya & Sera Ella
Hope this helps