If all you have are the death certificate and a marriage certificate for this person, that isn't very much to go on. You're setting yourself up for what one of our community members called premature connectivitis syndrome (PCS).
From his answer to Tracing US ancestor back to Germany?:
At one time or another, I suppose most of us have suffered from premature connectivitis syndrome (PCS)--we don't really know enough yet by which we can well identify a person, yet we want to connect them to a much earlier place in time.
Good advice from this answer which applies to work in any locality:
Work from a time line on which you specify locations (and/or events). Pick the point on the timeline where you feel you have solid information; begin there. When you move from that point in time, think INCHWORM (rather than leapfrog).
To this I would add: put all the records you have in their proper context. The site GenGuide offers articles about different record types and gives pointers to where records can be found.
Knowing who created the record and for what purpose will help you make sense of the information contained in the records, and you may notice clues that didn't seem significant when you went through the records for the first time. For example, you said:
Her father's occupation was listed as naval pensioner, but I'm not sure how far I can get with this.
GenGuide's article Royal Navy/Royal Marines - Pensions to the Wounded, Retired, Widows & Orphans - Ratings & Officers and TNA's guide Royal Navy ratings’ pensions 17th-20th centuries can help you find out if this is a line of inquiry you want to pursue. Consider 1) what information might be found in a typical record and 2) if this is information you want to know.
Rather than leaping from one unproductive search (for your relative) to another (for her father), try to look at the big picture as you contemplate a new line of research. How common is the surname in question? Before plunging into the records, do some preliminary searches and see how many possible candidates you have for your relative's father.
You don't say whether the marriage record under review is a GRO marriage certificate or a parish record. If you haven't already done so, download the GRO's guides for birth, marriage and death certificates from the FAQ - Most Customers Want to Know's section What information will I see on a birth, marriage or death certificate?. All three links are included here for convenience:
Where did the marriage take place? If the location is at a Registrar's Office, there may not be another record, but if it took place in a church, you may have opportunities to find more records.
Other research opportunities:
- identifying the witnesses
- looking for the residences of the bride and groom on electoral rolls or in other records -- do you know who owned those properties?
- studying the history of the town where the wedding took place.
It's crucial to know whether the town is a destination for out-of-town marriages. One clue from my own research came from putting together the dates of a married couple's possible marriage registration and the birth registration for their first child. Doing the math suggested why I hadn't found a marriage for this couple nearer their birthplaces.
If a couple were Non-Conformists or married in a large city that has special research challenges, it might be worthwhile to view classes via FamilySearch's Help Center Lessons. Understanding how far away from home a couple may have traveled to marry can help you decide how large a radius search may be worthwhile.
Becoming familiar with research locations is important. You may find some useful information in the answers to Determining what records are available in a particular locale? The local FHS (Family History Society) or the Society of Genealogists may have records that are not accessible via FamilySearch or the big subscription websites. Before you add any other subscriptions, learn to look over their holdings and evaluate whether the subscription will be worth it to you.
It seems counter-intuitive, but if you don't have enough information to go backwards in time, the best plan is often to start from where you are stuck and to work forwards so you can get more information. Does your relative have siblings? Very often we can't find the information about a person's parents or birthplace records about that person, but we have to use information from the records of siblings or other relatives.
The other thing I would advise you to do is to sign up for email newsletters and/or follow the blogs at findmypast, The British Newspaper Archive, The Genealogist, and AncestryUK. This will bring you news of new record sets coming online, tips for using the sites, and any promotions, in case you've discovered one of the sites has a record set you want to explore. The Genealogist's newsletter is especially valuable because they do Feature Articles about the record sets they publish, and you can learn more about the records. If you can access the sites at a local LDS Family History Center, use to learn them before you subscribe.
You already use FamilySearch for searching records -- but don't neglect the FamilySearch Wiki and the Lessons in the Help Center. If you haven't already done so, learn how to browse records (so you can explore the record sets which haven't been indexed yet) and how to use the Catalog.
Other things to consider:
- Learn how to do wildcard searches (each site may have different wildcard rules)
- Make a list of name variants and possible OCR glitches for the names you search (for printed sources, see 8 Ways to Overcome OCR Errors when Searching Newspapers to get tips)
- Do you know all the nicknames for your relative's name? She might be Margaret on one record or Peggy in another. In one case, I found a mysterious child "Robert" who was mentioned in no other record -- until I found his obituary and learned that my subject shared the same name as his father, and "Bob" was a nickname.
For each new record you find, ask: "Is this a record about the person I'm looking for, or someone with the same (or a similar) name?" I approach each new find as if it were about a same-name person until I've learned otherwise.
Finally, recognize that computerized databases have limits and weaknesses. Crista Cowan's video: Some Genealogy Records Have No Names demonstrates how records can be there, but a name search won't reveal them.
More things to consider:
- Check a library near you (or TNA's bookshop, or your favorite genealogy supplier) for a copy of Mark D. Herber's Ancestral Trails, an essential guide to British Genealogy
- You can trace Royal Navy personnel who are commissioned or warrant officers via the Navy List. See TNA's guides: Royal Navy commissioned officers, Royal Navy warrant officers, Royal Navy commissioned and warrant officers: further research.
- If you have death dates, check the National Probate Calendar for the primary parties in the marriage, the fathers of the couple, and all witnesses, to see if anyone is mentioned. You can search for free: Find a will or probate document (England and Wales). Bear in mind that probates may not happen immediately after the death -- sometimes it can take decades for the probate to complete, and there may be one grant. I search at Gov.uk, Ancestry, and findmypast to take advantage of all three search engines, and to compare image quality of the calendar entries, but always check Gov.uk in case there are handwritten amendments to the entry that aren't shown on Ancestry or findmypast.