I have been working on family history for more than 10 years. IMO Ancestry is the best but if you want military history then findmypast is better but both come at a cost. If you have the time and can get to London much of what is available on websites is available at Kew and through the GRO. Before 1840 then you have to work from parish records. Many of these are slowly coming on-line but the best source is the local Public Records Office which is free to use.
I have found that the Church of the Latterday Saints had little of use but that may be specific to my family.
Be prepared to search using alternative spellings of first names and surnames. You will almost certainly come across gaps. I have a mystery which after nearly 20 years of research I cannot solve.
Be warned once you start then you will be hooked.