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New staff

Changing staff every time you level up is expensive and in my opinion not cost effective, especially in your first two or three seasons when you may be levelling up more than once in a season. Good Chief Designers (CDs) are scarce and if you decide to edit the strength and weakness it could well cost you 100 tokens.

Early in your iGP career you are likely to be in either a Rookie or Pro tier so the competition will often not be so fierce as it will be when you promote to Elite. In these lower tiers it is not essential to have the very best staff at any cost, you should be able to achieve good results with staff as much as two levels below your manager level. 

Chief Designers:
I prefer to do nothing during the season and spend the couple of days between seasons scouting for a good CD. If you are lucky enough to employ a good one you can leave and re-join your league during the break and the resulting car design at the beginning of the season will be as if you had employed that CD for the whole of the previous season.

Technical Directors (TDs):
As Bruno says, low level Technical Directors will reduce your research power. You will need to decide whether or not it is cost effective to replace them every time you level up. There are a couple of things to consider...

• Do you have one of the highest designs in your tier?
  If the answer to this is "Yes" a higher level TD is not going to yield much in terms of additional research design points.


• How far through the current season are you?
  If you're towards the start of the season you will have to live with a reduced research power for a lot of races so it may be cost effective to replace the TD now. If you're towards the end of the season and designs of all teams are at a fairly high level it may be better to wait for a couple of races until the season break.


• What level are you?
  As I said above, lower level teams level up frequently, especially when there is a high level team in your tier. In these circumstances, unless money is no object you're probably better off skipping TD recruitment, maybe replace the TD every second or third time your team levels up.
  

Doctors:
This is one area where in my opinion the level you are at is a very important factor. When you eventually get up to the higher levels and your drivers are fully trained you can save money by dispensing with a high level doctor. Just let your Doctor's contract expire and the game will automatically assign a very low level doctor to your team and wages will only be £50k per race.
Early in your iGP career when you are trying to get your driver(s) trained as quickly as possible it is often a good idea to employ a Doctor the same level as your team. However, if you're really struggling with finances this is the first area I look at because it's an easy way to cut costs.

Yes, I'm locked down and bored :-)

Reason for edit: Typos.

With all staff you can ignore Talent, Experience and Morale, the important attributes are level and star rating. The star rating is just the level of the staff expressed as a comparison to your Manager/Team level. As an example your L6 CD Aleta appears as 1.5 stars to my L20 account whereas for your L6 account she appears as a 4.5 star and will produce maximum design points for the following season.

Her strength in Acceleration is good but her weakness in Handling is not ideal.

The important attributes for CDs are level, strength and weakness.

The level determines the number of design points the CD generates every race towards next seasons design. The strength will result in a higher value for that design attribute and the weakness will have a lower value. 

CD Strength and weakness also influence research in the current season. If you research CD strength you get a boost of approximately 10% on your design strength but for weakness your design strength is roughly halved. So only ever research your CD weakness as a last resort if nothing else will yield any points.