How much i save in 300 riyal ?

You can live cheap and save good money

OMR 300 is a blue collared salary. You need to think wisely before entering into a den.

Is in hand salary 1400 OMR is sufficient for Family (2 adult and two kids) to live and work in Oman? is enough saving can be done if we live modest lifestyle.

Food expenses will cost 35 to 40 rials
Phone and internet expenses are bit costly in oman
Broadband will cost 25 rials per month
Normally in bachelor acomodations  3-4 people share wifi connection and share the expense
Mobile and data plan will cost around 10 rial per month
apart from this other personal expenses will cost around 10 rials
With sharing wifi total expense per month will be around 65 rials
If wifi sharing not available then 85 rials

Movie tickets rates are 2 rial to 3.5 rial.Add this to total expense

Since your accomodation is already included and I suppose you are going to stay alone. So the very conservative calculation says you will be able to save approximately 175- 200 RO per month.
50-75 exp on food
20- 30 on Mobile/internet
Miscellaneous 35-40

Welcome to Oman