Again, depending on severity of your iron deficiency, you need certain amount of iron. That's why it is so important to take the iron under your physician's supervision.
To give you an example, the iron content of a Ferrous sulfate tablet is 65 mg, whereas the iron content of Ferrous gluconate is 39 mg, there are other preps that have more dosage of iron for the more severe cases of this deficiency.
In the market there are a number of other compoundings of iron sold. Some have "absorption-enhancing" substances such as ascorbic acid and amino acid. There are some that are advertised as delayed-release, to prolong the iron absorption over several hours.
One point to consider is that to cause the tablet to be more absorptive, tend to increase the gastrointestinal side effects.
So, what I suggest is to find out how much iron you need and accordingly provide your body with the correct amount.