I joined a team towards the end of the last season. It has some benefits, but not a massive amount.
For my £3million, I'm in a team with 1 pro, a few amateurs and a few rookies. We've got an off-site team forum, which is rarely used and doesn't have as much info as I'd like, and the team leader usually sends a message around before a race summarising how the rest of the team got on last time, gives a manager of the race award, and sometimes his thoughts on the next race. Unfortunately our team leader is only in rookie, and isn't massively successful, so his thoughts are usually only good for a starting point for setting the car up.
On the other hand, I made just over £1m in team earnings last season, so if you stay with a team long enough you'll make money out of it. The team leader has supporter status, so he's helpful with trying to find new managers, especially now database spiders are banned. (Incidentally, if anyone can work out how to use the files available to import the driver database into excel, let me know?) There's a couple of Russian guys in my team who managed to procure quite a lot of info from a dodgy Russian forum which got shut down, so they are quite knowledgeable. Overall I'd say it was worth it, but it wasn't as great as I was expecting. If this forum wasn't so visible to anyone searching for game data, it'd be nice if we could share more info between ourselves on here, what do you guys think about that?
It depends on the team though really! I'd at least expect a team to be able to offer you the wing split for each track (I'm working on getting that from mine!). Some teams I know have developed tools which can predict your perfect set-up from driver data, car parts and the track in question, so you only have to do a single practice lap to check it (saving £350,000 a race), and I've heard about very advanced race strategy engines which skirt around the edges of what real racing teams will do (game theory,etc). However, teams with those sort of tools are unlikely to be recruiting, and if they are, competition will be fierce.
As for the race, from the fuel data I've got, I'm in a bit of a sweet spot in that the fuel needed for the full life of the wet tyres and soft tyres is very similar. I've set the fuel for that, so I'll always be able to get the maximum laps out of a set of tyres. My driver is pretty handy in the wet it seems, and the pit time is short, so I'm planning on pitting for every weather change. If it's wet early on and then dries up, I should only need to pit once more for tyres. For the car set-up I've compromised my dry set-up about 20% towards wet.
Sorry thats a bit long!