Depends on the campaign (doesn't everything?)
If you're running a fantasy/high-magic campaign, don't use GURPS Lite. Don't use GURPS Basic. You'll need GURPS Magic in addition to the 'core' book Lite/Basic.
Sci-fi can work with just Lite/Basic, but I'd consider investing in Space or Ultra-Tech: neither Lite nor Basic has enough material to cover it unless you want to do a *lot* of paperwork inventing and converting things.
A 'real' medieval setting or a modern setting can work with Lite or Basic. Basic is better, particularly with roll-players or if you intend to use advanced combat rules. Since Lite is found in the back of sourcebooks, unless you intend to use these sourcebooks, Basic is the better investment.
Any other setting will probably need the appropriate sourcebook, though a determined GM could struggle by.
If you're running a fantasy/high-magic campaign, don't use GURPS Lite. Don't use GURPS Basic. You'll need GURPS Magic in addition to the 'core' book Lite/Basic.
Sci-fi can work with just Lite/Basic, but I'd consider investing in Space or Ultra-Tech: neither Lite nor Basic has enough material to cover it unless you want to do a *lot* of paperwork inventing and converting things.
A 'real' medieval setting or a modern setting can work with Lite or Basic. Basic is better, particularly with roll-players or if you intend to use advanced combat rules. Since Lite is found in the back of sourcebooks, unless you intend to use these sourcebooks, Basic is the better investment.
Any other setting will probably need the appropriate sourcebook, though a determined GM could struggle by.