Gradually
Steadily, Quietly, Slowly
adverb, の adjective
If you do it gently gently then you're only doing it gradually. You have to go slowly if you want to be as gentle as possible.
じょじょ
The reading is just the on'yomi readings (which you learned with the kanji) twice in a row.
二学期に入って、徐々に成績が上がり始めました。
Second semester came and my grade slowly started to rise.