I will spend 2.5 days in Belfast and one day in Dublin. I also want to travel a bit while staying in Belfast.?

I wanna stay in hostels and travel by bus between the two cities. Where should I stay? Where should I visit? Is there any dangerous areas to avoid ? How should I spend the 3.5 days? Many thanks

Belfast is far more interesting than Dublin. The Farset Internation Hostel is very clean, its about 拢20 a night for twin room but more like a hotel than your usual hostel.
You can get black taxi tours around the republican areas and murals in Belfast which i'd recommend. There would probably be similar things in Loyalist areas.
If you are going at beginning of August the West Belfast festival is on so a trip around west Belfast is a must.
The flags and paintings will tell you if you are entering a republican or loyalist area.
You might want to travel up to Donegal to the Gaeltacht areas where Irish language is spoken. This would be 2 or 3 hours from Belfast on bus.
Dublin is more expensive than Belfast and far more touristy. Belfast is more "real". There are lots of hostels in Dublin but book before you arrive as finding one is a nightmare.

I wanna go too. Take me with you.

Avoid North and West Belfast at night they can be very dodgy!
You should spend a day travelling to the North Coast (Giants Causeway/Bushmills etc) and go to Stormont to see the buildings etc there (try a sightseeing bus from Castle Junction in the city centre)

Check out the backpackers hostel in the Donegal Road Sandy Row area and try and stay away from west Belfast at night it can be a bit dangerous if you don't know where to go also try the Belfast bus tours they do all the areas of Belfast and the welcome centre in Donegal Street facing the city hall also go on the city hall tour you will get information in the welcome centre and if you get lost ask anyone on the street and they will be glad to help, the translink bus stops are all around the city hall and all the stops have a map on them with times of bus numbers and route etc