Help me with my Europe itinerary

I’m currently in the early stages of planning a solo trip to Europe. I’m 22M from Ireland and I’m hoping to spend 4-6 weeks interrailing, beginning on August 2nd.

5k budget, not including flights and interrail pass.

Trip will hopefully consist of a mix of exploring cities and hikes, but I have not booked any activities yet.

Current plan;
Brussels -3 nights
Rotterdam -2 nights
Amsterdam -3 nights
Berlin -6 nights
Prague -4 nights
Budapest -3 nights
Zagreb -1 night
Split -5 nights

From here I dont know where to go. I could call it off and fly home but I will have another two weeks before I’m back in college which I would to spend between Rome, Barcelona and Lisbon but the travel times are putting me off.

I have booked a flight the flight to Brussels and purchased an interrail ticket .

I plan to have all hostels and transport booked in the next couple of weeks.

Any feedback or help will be much appreciated.

Cheers lads

Help me with my Europe itinerary