Pretty long story! My first encounter was probably back in 2005-6-ish, when I plyed a bit of Melee at my cousin's house. I played Kirby and Luigi. I sucked. My only opinion on the FE characters at the time was "who the heck are these guys." Then I went home, and didn't touch a Smash game for years.
About four to five years ago, my friend revealed to me that she owned a copy of Brawl. Absolutely delighted at the fact that I felt like I've rediscovered part of my childhood, we played every time I went over to her house. Now, I initially mained Meta Knight, but she mained Marth, and ater a while, I shifted to Pit- Then finally shifted to Marth after realising that I was, indeed, best with the japanese sword guy. About a year later, I looked into FE as a whole, saw that Awakening was a Thing that Existed, but sadly, I didn't own a 3DS because handhelds were apparently bad for my already not great eyes. I did, however, own a Wii, but at that time, I wasn't aware of RD's existence.
Then my pal got Awakening. I played on an empty save occasionally, so Awakening indirectly counts as my first FE, but I din't get too invested yet. Then, two years ago, my father went on a trip to the US. I asked him if he could get RD or PoR for me. Ater what apparently was a massive ordeal that I didn't know would happen, my dad managed to fish out a used copy at GameStop for sixty bucks.
I was absolutely delighted. The game was love at first sight. Even though I died a lot and had to reset every second level.
That aside, I really don't think Radiant Dawn is a good place to start out at. I had to give up on my first run because I screwed up on leveling everybody decently during part one big-time. To the point the DB would've gotted decimated by the GM once those chapters rolled around.
When I finally figured out how to play FE properly, though, I got overly attached pretty quickly. Now I'm neck-deep in heck and can't get out.