There have a lot of places in North East India to travel. Kaziranga National Park
Tsomgo Chho
Goecha La Pass
Nathula Pass
Tawang Monastery
NohKaLikai Falls
Shillong
Gangtok
Guwahati
Agartala
Pelling
Manas National Park
Zero
Cherapunji
Kamakhya Temple
Gurudongmar Lake
Elephant Falls
Fashion View Point
Orang National Park
Laitlum Canyon
Peacock Island
Kynrem falls
Ban Jhakri Falls Park
Sungester Lake
Starting with Meghalaya here are some beautiful spots Mawlynnong village
Jampui hills
Anini
Jatinga
Phawngpui park
Andro village
Pelling Goechala Majuli island Durylang hills
Mon
Shillong
Cherrapunjie
Tawang Loktak Lake Ziro valley
Kaziranga national park
Manas National park
Unakoti Tripura Bala Sundri temple
Ima Market Imphal Kohima
The answer to this question will depends on many factors like: For How Many Days you want to Travel?
You want to Travel Solo or Family?
You are travelling in own Vehicle or Public Transport?
You want to go to see Mountains or National Parks or Trek ? I have visited almost whole of North-East Feel free to DM to ask more. ==