The first game often requires to find hidden staircases which you find by jumping around. It helps to get the sandals because you can make longer jumps and thus a greater area will be covered as anything under your jump counts as "checked for secrets".
I think it's a great game however once you start getting into the levels with insta death pits you can easily get frustrated because you fall *on* the edge of platforms, not after; and dying like this makes you lose all your power ups. Some levels have a lot of jumping around pits.

2 doesn't have this problem (less pits and they are more forgiving) and doesn't require to find secrets or at least nor nearly as many, and you'll probably like it a lot better. It's basically the template for the SFC games. Even if you give up on 1 you should give that one a try.

I enjoyed the 2 RPGs but they're fairly basic and I'd only recommend them to someone who's either a huge Goemon fan or a huge Famicom RPG fan. In the first special moves are almost never worth usings so it's all "attack on loop". The first game is a bit better but overstays its welcome imo. They both shine through their presentation and humour though, in Gaiden 2 you can play as Simon Belmont for a short while for instance.

Pretty sure everyone's going to tell you to start with the SFC games but that none of them have played the FC games btw.