By all means get yourself in good shape, but if your weight is not extreme it shouldn’t make much difference.
Do get started on the folic acid.
If it helps you to feel in control, you can start tracking your cycles to look for when ovulation occurs (although you absolutely do not have to do this if you don’t fancy it, but it might keep you busy!): day 1 is the first day of your cycle. Make a note of days that you get EWCM (completely colourless, wet and stretchy when you wipe, as opposed to white or creamy and sticky). These are usually the fertile days of your cycle. You can also use OPKs (you can get cheap packs of 50 on Amazon) - basically you pee in a cup and dip them in once a day from a couple of days before you think you’ll ovulate (say, day 11), look out for signs of a faint line which will usually become a dark line 24-48 before you ovulate. You can also track your basal temperature first thing in the morning (literally first, before you get out of bed). A change in temperature tells you that you ovulated about 3 days ago.
Any/combination of/all of these methods should give you a good idea of if you ovulate at the same time in your cycle, and of anything that might be problematic e.g. short luteal phase (gap between ovulation and period of less than 10 days). Ideally, you dtd every 2 days from 4/5 days before you ovulate till 2/3 days after. Generally accepted wisdom is that correctly timed dtd gives you 25% conception in each cycle.
But it could take a while and these things can drive you insane, so maybe do none of the above unless you have trouble!
Egg count etc is unnecessary unless you have specific issues.
Good luck to you 