pensioen build-up

As an expat I have gaps within my pension scheme and as I had different schemes in different countries (Netherlands, UK and more likely to come) I will also lose money (administration costs etc) for transferring one pension scheme to another.
Can anyone give me advice, or do you know someone how could, on how I can address these issues so I make sure I save enough for my retirement?
For example I’m wondering whether I should stop my current and future employers pension schemes altogether and arrange for my own pension savings so I am independent of future employment. For example I could invest in property for me and my family to live in or for renting out as a landlord.
Regarding the latter does anyone have any good advice on how to buy a first property in Bristol as an expat with little savings?
In other words:
As expat I am and will work for different employers and different countries with all different pension schemes. Does anybody have any financial advice on how to best arrange my pension build up?