My girlfriend from the uk and I want to get married, would it be easier to get her here first and then marry her and what will we need?

The question is not what is easier, but what is legal. If you and your girlfriend from the UK have a preconceived plan for her to enter as a tourist and then adjust status while she is here in the States, she would be open to a charge of misrepresentation in representing herself as a tourist when she was actually planning a permanent stay. If on the other hand there is no such intent and while she is here you both decide that you should marry and she stay, there would be no misrepresentation. Other choices are your applying for her under K-1 fiancée status which would take approximately 7 – 9 months to complete or applying for her under an immigrant visa petition if you marry her in England which would take approximately a year. Due to the limitations of the Lawyers.com Forums, Alan Lee, Esq.'s (the "Firm") participation in responding to questions posted herein does not constitute legal advice, nor legal representation of the person or entity posting a question. No Attorney/Client relationship is or shall be construed to be created hereby. The information provided herein by the Firm is general, and requires that the poster obtain specific legal advice from an attorney. The poster shall not rely upon the information provided herein as legal advice nor as the basis for making any decisions of legal consequence.  

I recommend that you bring her here on a fiance visa and marry in the US (assuming you want to reside in the US).