[Ashus]

I've gradually developed the following strategy to win any special event in NFS No Limits.
Of course sometimes you need more skill, sometimes you need luck and it never hurts to have some gold from Daily assignments if you lack skill or luck (500 gold should be enough reserve at most times).

In all races you need to drift/draft/near miss at all times to get maximum credits to make things easier. Remember that drifting almost straight ahead doesn't slow you down and earns you nitro. If you can choose to use nitro a little bit later on straight roads or to drift sharper corners, do that; otherwise use nitro straight away.

If you are racing a special event from the Vault, there are no credits when you lose a race. In live events though, find a race of the day that gives you most credits by drifting and drafting at the same time behind another racer (fail2win). I found the best to be nitro rush with multiple racers (drafting without using collected nitro) or rush hour. Fail on that repeatedly with at least 1500 credits per try.

Repeat races retries can be replayed another day counting from GMT midnight, so in Czechia it is at 1:00 in the night when CET is active and 2:00 when CEST is active (central european summer time). Start the event at 15:30 GMT (17:30 CEST).

The big picture is you want to finish with a car upgraded completely to higher color. That saves you the trouble of having to grind enough materials and a lot of cash to upgrade from one color to another. In every event you upgrade the whole set once and receive 2 upgrades kit. Usually they are from acceleration and nitro category. Take a note which upgrade parts you already bought, from day 4 you might get confused by looking in storage as bought ones get mixed up with the ones you won. Use all available tickets before you go to sleep and do the same when you wake up; you need as much credits as possible.

Strategies differ a little for live and vault events.
Live events:

Day 1 and 2: Find the best fail2win race of the day, don't finish the day and do not repeat the last race in case you win by accident. Repeat fail2win race. Now look into store every hour if there is an upgrade kit. If you see one you haven't already bought and you have at least 8000 credits, buy it and pay the rest with gold. As the day ends, finish races successfully by taking into account you want to start collecting tickets and have 4 of them ready when another day opens. Day should be completed with 0 tickets at 12:00 GMT (14:00 CEST).

Vault events:
Day 1 and 2: Maximize the credits and buy one upgrade kit with credits and gold. You often don't need to insert won materials at the end of day as you want to spend as little gold as possible.

All events:
Day 3: There are first repeatable races here. Unlock first two replayable races and repeat them until GMT midnight or you run out of them. Keep on looking into store for non-bought upgrade kits. When you wake up the next day, finish the day and then find the best fail2win race among repeatable races. Finish it only twice and keep failing until you need to start collecting tickets like in day 1. If you have exessive amount of credits, you can start buying flywheels or thrust sleeves. Prioritize speed category to make your races easier and to overcome PR locks.

Day 4: There are more repeatable races from now on. You no longer need fail2win, you can just keep winning repeatables from day 3 when you run out of those in day 4. Keep looking for missing upgrade kits. Prioritize speed upgrades and 4000 credits gray materials.

Day 5 and 6: Just race. Now you need to focus on balancing the upgrade states of all parts. When given a choice, repeat race from later days as they give more credit. If they are too difficult (eg. breakouts with requirement to takedown cops) and the risk of losing is too great, repeat any race with required materials in them. Keep looking for missing upgrade kits.

Day 7: This day gets unlocked with day 6. Start it as soon as you can. Examine awards for races in this day. There are some upgrade kits - you don't need to look out for those anymore. When you hit the PR lock in half of this day, look ahead for awards in races and determine what number of what material you still miss. Go repeat those races to maximize the probability you wouldn't need to buy them while not having more of them than needed to upgrade color. Also use any credits to buy any materials you need. Remember - at GMT midnight, repeatable races get reset. Gradually finish races and wait before the last race. Complete upgrades for all parts and finish with flying colors.

If you stumble upon an idiotically unwinnable race, you must not waste too much time on it. If the race looks to be winnable after severals repeats, do that and even buy tickets. It is usually cheaper than skipping race with gold. Sometimes you just need a faster car, so don't hesitate and repeat some older races to upgrade sooner and return to the story after that.

This strategy can make you win the 7-day event in 6 days and one morning (6.5 days). Depending on how much time left in the event you have, buy more tickets. If you haven't made a big error, do what you can to finish the event as you don't want to waste another week of your life, even buy some materials with gold or finish without completely upgraded color.

Lastly, group a live event with a vault one when possible and play them together. That way you can rest every other week and not look for upgrade kits in your sleep.