First time interrailing, need advice.

I posted this in r/Interrail too, but would love to get your input as well!

Hi,

Me and five friends are going interrailing for the first time and as we have started doing the math, we are feeling a bit overwhelmed by the costs. We are looking to get some wisdom and tips from the experienced travelers in this sub.

• Duration: 15-16 days
• Time of the year: Early July
• Route: Starting from Sweden > Amsterdam > Interlaken > Milan > Rome > (by boat Ancona- Split) Split > Ljubljana > Budapest > Vienna > Prague
• Our target budget: We were initially hoping to keep the total cost for the trip around 2500 euro per person.

We have started looking into accommodations and activities to get an estimate on the cost, but the cost is looking unreasonably high compared to what we have read from other travelers. (Disclaimer, we have a prima donna that won't have a shared bathroom with randoms.)

A few questions we have:

• Is it better to book Airbnb's and hotels in advance or just days before arriving?
• How much did you spend on food per day?
• Should we reserve all seats way before? Even optional?
• What are you general interrail tips?
• What rookie mistakes should we avoid?

Any tips on how we could bring the total sum down would be highly appreciated! We really appreciate any advice, budget and general. Thanks in advance!