I am murderous on tyres so I am not a fan of "saving" them, especially at crazy high multipliers.
The FIA race was soul crushing, by lap 5 on the mediums my times were dropping like a stone.
I was the same exact way. I've been playing for 3 years now, and I avoided daily race C's for almost 2 years because I was afraid of tire wear and I found the whole strategy thing just intimidating. I remember the first daily C I did. It was a good week of combos but all the forum was talking about was strategy for race C.... which was a high tire and fuel multiplier at Brands Hatch in Gr.4. No-one wanted to talk about race B and it looked like everyone was having a blast at Brands. I then figured if there was as good as time as any, I needed to take the plunge on this one. Not to mention Gr.4 at Brands is probably my best combo on this game. I remember I even did a few custom races in arcade mode with high multipliers just see what going through the pits were like and how to select tires and refuel. Come race time, I had a blast. After that, I still only did Race C on rare occasions, but my cherry was popped nonetheless.
However, I still avoided FIA like the plague. That was until about 9 months ago or so (maybe a year..not sure) when all of Super GT's youtube vids were FIA races. It looked like a lot of fun. So I started watching the FIA thread, and to be honest..... I started feeling left out watching everyone post up their liveries for the season, and reading their stories and looking at their screen shots of their results after a round. So, I looked at the schedule and as luck would have it, another combo that I'm really good at (Dragon Trail Seaside in GR.2) was the nations race the next day, so I immediately stopped doing daily's for the day and ran custom races in arcade mode to prepare. I even made my first livery for a car just to be part of the in-crowd!! Come race day it was a lot of fun, and it didn't hurt that I won too!!
Now I almost exclusively do Daily C and FIA. With FIA, it has opened the game up for me more..... left me more to do. If I get bored or don't like the weekly combos, I have that weeks FIA races coming up. And there's always next week's rounds to practice for. Plus, its really broadened my horizons on all the different cars in this game and their strengths and weaknesses. I'll look at the schedule, and really put in a lot of time to figure out which Manufacturer I want to go with for the season..... taking in account the different tracks and the multipliers given for each race. I really geek out on that stuff. Before I got into FIA, I only used 4 cars no matter what. The Beetle, the 911 RSR, the slophy, and the TT. And over time it just became the Beetle and the TT because I actually learned how to deal with the dreadful FF understeer. Now I look at ALL the cars, and if there's a daily combo I don't care for, I jump on the Alt and use it as practice and a testbed for either upcoming seasons, or my various manufacturers spread throughout my 3 accounts.
And FWIW, learning how to save tires actually made me faster. It forced me to make good inputs and focus on line selection a lot more