Hi Hayley,
We work with a lot of clients on this kind of thing. I'd recommend a few things:
1. Consider how you can leverage existing data sources, there have been mentions in this thread about internal data warehouse, etc. and even how you host your forms externally. So figure out what data sources you have internally that you can use (and trust) to fill in gaps.
2. If you are planning to use a data append vendor (and there are many to choose from), figure out what makes sense for you. Is it a full database append? Something someone like D&B, ReachForce or NetProspex can offer you. Or is it a matter of getting more data about the people who submit your forms (and finding a solution like ReachForce SmartForms or DemandBase)? Or is it both? Determine what matters and where you can get the information as well as the best strategy for ensuring you get the biggest bang for your buck.
3. Build processes inside of Eloqua to bring all of this together. Create standardized values, use Eloqua to align the data you get to those values and then make sure your segmentation, programs and lead scoring programs are aligned accordingly.
Also remember, once you've got all of this in Eloqua how do you share it in your CRM?
Hope this helps, feel free to DM me if you have any specific questions.
Best,
Lauren