Resident Doctor Salary in Saudi arabia

MOH KSA salary is calculated approximately as follows
Resident Basic Pay 4000 per month
Per year Experience 200 /year so in your case 4000 +1000=5000 d be current basic pay
You d get 20% allowance on 5000 which is 1000 per month
Travelling allowance 400 per month (if through MOH recruitment if private then some don't give this)
Another allowance 15% is given on current basic pay which in your case d be 750
Total take home is current basic +20%+15%+400
5000+1000+750+400=7150 per month
House rent or badal sakan is 3 basic salaries 5000x3 15000 per year is separate than this

Thanks.

Any idea how much I can save per month out this salary? And can I get a desent accomodation on 15000/year?

Accommodation and expenses are related with the size of the family. If you d come with family and kids then it d be very difficult to save substantial amount of money.
Housing again depends on the city in which you d reside but usually you can rent a good apartment in 10k per year in an average city.