Hello ​@Anis Asea 

It is difficult to answer this question. What are your interests? Big cities with cultural offers (museums, monuments) or beautiful landscapes? Do you prefer the North or the South of Europe? The West or the East?

There are some good suggested itineraries here, which you can use as a base to make your own plans.

https://www.interrail.eu/en/plan-your-trip/trip-ideas
 

Like ​@Danhiel says, it’s difficult to suggest anything more without information on what you like doing, your budget, and specific places you want to include.

Google Flights has a good map based search, where you can search for flights around your dates, and scroll around the continent to find a good one.

Thanks for the suggestion. I already looked into that before creating this topic but the thing is it doesn’t have ones starting from northern europe all the way to west. It’s on me on not suggesting much info but countries I definitely almost wanna cover most top cities in western europe. But also some of eastern europe like poland,hungary etc, I do have a question when making the trip planner, Does anyone know to get to croatia (Zagreb/dobrovnik) the best possible routh from which country?

All the big cities in Western Europe are well linked by train. You won't have to time to do everything.

I would remove Spain as trains are infrequent + reservations are annoying. But then... do some homework! You can do the classical Amsterdam-Belgian cities-London or Berlin-Prague-Budapest but there's so much more.

Only thing I'd recommend: catching the Malmö-Berlin SJ or Snälltåget night train to start the trip.

Zagreb has 2 mainlines: from Ljubljana with few trains/day and from Budapest with a single daily train. It's not much but already way better than the Balkan neighbours!

Dubrovnik does not have a train station. You can take a train from Zagreb to Split and continue by bus (not included/no discount).

I just created my travel plan and looks like I will probably need close to 2 months. But I’m planning to start  ‘most’ of my trip in Milan cause it connects and covers most the countries I want to go to. However, I want to know lets just say I go to stockholm from gothenburg cause I got friends that want to go there, so I started the 1st travel day in gothenburg then spent couple days in stockholm and took a flight from stockholm to milan. Will I have any issue if I start 2nd travel day in Milan even though my last travel day was from GOT- Stockholm if that makes sense?

Not an issue.

You can always use one of those itineraries for inspiration, and piece together your own trip to fit your requirements.

Don’t forget, you don’t need to decide it all now. Maybe start by getting a few key journeys and cities decided now, and some of the rest you can decide much later.

One of the major benefits of the pass is that you can literally wake up in the morning and decide ‘maybe I’ll to Prague today’!