I am new to the 2 stroke and just picked up a 72 dt2 250 and have looked all over for what oil to put in the oil tank and can't get a good answer so would someone please help 

 from near Salisbury, UK.

I usually use whatever semi synthetic my dealer has in stock.

I believe that mixing mineral with fully synthetic should be avoided, but others will confirm this (or not!).

Yamalube 2S seems to work for a lot of people, including myself.  But any two stroke oil rated for use with oil injection should be fine.

I have been using Belray SI7. Its available locally and is a nice high quality oil.

Yeh ,any semi synthetic, Carlube/castrol 2T,/Motul .its all better than the old Duckhams from the 70"s

I think having the oil pump and carb properly adjusted is way more important than the oil brand. Just use whatever smells nice to you, in the colour that you like! Going forwards a good simple health check is to see that the pipe doesnt smoke too much, these modern 2T oils are way less smokey, and every now and then pull the plug and make sure you have that coffee/toffee/light milk chocolate colour. That's usually my base health check.
Having oil in the tank of course and never let the carb run dry or you can do some nasty damage.