aahhhemm ... mech mods are for experienced users...
since you have very little experience with vaping a good suggestion would be to look into VV/VW ( variable voltage/variable wattage) types of battery/power supply for your first unit. As far as the top part ( atty) consider looking into a tank style unit with replaceable coils ( premade)... unfortunately there are about 5000 different setups one can configure with all of the different parts available...
take some time and do some Youtube watching of Vape Reviews, browze some websites which sell the items to get an idea of costs and general knowledge of the parts... Fasttech.com is one such site, but be prepared for information overload
do you have any friends that vape?? if so maybe you can borrow one of their backups for a week or 2 to see if you really want to enter this venue before dropping the cash... it can get pricey... a decent setup can run around 100$ usd from online, if you buy it at a vape shop you can pretty much double the price...
one of my long time favorite setups is the SVD from Itaste, the RSST atomizer, VTC4 batteries (3), and an Intellicharger dual bay ( charges 2 batteries at a time)
you will see plenty of suggestions on what to get....