It does not matter how much iron or dilute sulfuric acid you use, using more of each will just give you more solution.
Dilute the sulfuric acid to around 10%, get some clean soft iron (not steel) transformers laminates make a good source for soft iron, you can use a grinder to cut the welds, separate the thin soft iron laminated iron plates, and torch them with a propane torch to burn off oils, shellac... wash them in water and cut them to small pieces with tin snips, add a hand full or more to a Corning pyro-ceram ceramic dish on an solid electric burner of the hot plate, add the 10% h2SO4 and heat this, the iron will dissolve in the dilute sulfuric acid forming a green solution of FeSO4 (copperas) (iron sulfate), after you dissolve the iron cool and filter the solution, you can use it this way as copperas or store it.
Lou suggested adding a clean oil free Nail to keep the solution more fresh in storage (some free acid attacking the nail to keep it fresh), for storage or to make crystals.
I personally prefer to crystallize the solution for storage and to use the concentrated liquid or crystals from that for a reagent or use the crystals for testing for gold.
After filtering return the solution to the clean corning ware dish and use heat to concentrate and crystallize the ferrous sulfate to crystals, and a concentrated green solution, spooning out salts as they build up, in storage keeping the crystals covered with the concentrated acid in keeps the crystals from being in contact with air during storage so the stay fresh ,store in an air tight container, (HDPE plastic bottle works well), adding a few drops of dilute sulfuric to help keep some free sulfuric acid, helps also to keep the crystals fresh (and bright green).
Copperas crystals in air over time can oxidize to a brown iron oxide which will not work to precipitate gold or test for gold.
Keeping the crystals covered in their own concentrated solution helps to keep air out and the crystals fresh, a few drops of H2SO4, gives some free acid which also helps for a long shelf life of your pretty green Iron salts.
I have never tried adding a bit of iron and have seen no reason to with the way I store mine, (it stays good for me the way I store mine) but it would be a good idea to add a clean nail.
After decanting and filtering and crystallization ,you can redissolve the crystals a second time in dilute sulfuric acid, (filtering the re diluted solution again), and recrystallize it the second time for very pure ferrous sulfate crystals (or copperas crystals).