I find advancement to second rank quite confusing too.
I am unsure how to handle it and how it goes.
Can someone explain it simply…starting from the created character who earns his/her first experience point?
Its a big topic, and I'm not sure what exactly you are asking for. I can give you some additional information, though.
1. Each career has (about) 10 advances listed on it. Those are the maximum "in-career" advances that can be bought. Now, when I say maximum, the meaning is that that is the maximum number of advances that could count towards the 10 required to complete your career.
For example: Say a career as Wounds: 1 listed on it. If you purchase +1 wound during first rank, you would write that down in the Open Career section of your XP/Advancement sheet. It counts as one of the 10. If you wish, you could theoretically spend additional XP to purchase a second Wound. However, since your career only has a single "in-career" Wound advance, this second Wound purchase would not count as one of the 10 XP advances required to complete the career.
2. All careers are required to take 4 specific advances: a Wound, an Action, a Talent, and a Skill. They are listed specifically on the character sheet Advancement section. These do fulfill and count towards the career maximums, as well as the 10 advances required to be able to complete an advance.
3. Most career transitions actually happen when XP is at 11 or 12, and not 10. While 10 are required to be considered to have "completed" the career, there are additional costs. First, to get the dedication bonus for the completed career costs 1 XP. Then, transitioning to the next career might (or might not) cost additional XP, depending on the PCs race and the trait difference between the current career and the intended career.
I'm here at work, and so don't have an actual career card in front of me for a specific and realistic example to give you. I can give you a hypothetical example, however.
Traits: Basic, Rural, Menial, Rogue
Primary Characteristics: Strength, Toughness
Career Skills: Athletics, Resilience, Folklore, Nature Lore, Observation
Action - 2
Talent - 2
Skill - 1
Fortune - 1
Conservative - 1
Reckless - 1
Wound - 2
Bob decides to make a character. He chooses to be a Gardener career. I'll skip over character creation. We'll just assume (for simplicity) that Bob chose to spend 0 for starting skills so he has no previous training.
Appropriately, Bob also names his character with a powerful name, "Bob".
Bob plays a session and gains 1 XP at the end of the session. He is now the proud owner of a single XP. He now needs to decide what he is going to do with that point. He has several options.
1. He can spend it to buy 1 advance that is "in career", since those cost 1XP each. Since he has not taking any advances yet, he could therefore buy anything in the list of Advances available.
2. Bob could save the XP. This could be used to buy an advance that is NOT a career advance, such as a skill that is not a career skill, or he could save it up in order to purchase an increase to one of his career's primary characteristics (which take a number of XP/advance slots based on the new value. i.e. raising Strength from 3 to 4 would cost 4 XP and use up 4 Open Career slots)
Bob decides to buy a skill. He spends his 1 XP on Resilience. Since Resilience is a Basic Skill, this counts as Training the skill, and Bob checks off the first box under Resilience. If Bob had had Resilience already trained, then he could have instead purchased a specialization for Resilience (specializations require the skill to the trained before they can be purchased)
On his character sheet "General Career Advances" section, under the "Skill Training" line Bob would write "Resilience".
Bob plays a second session and gains a second XP. He again faces the choice of what to spend his 1 XP on. This time, however, there is a slight difference. Since his Gardener career only has a 1 next to skill in the Advances section, if Bob were to want to take a second skill it would not count. As long as the skill was still on the career skills list, the skill still only costs 1 XP. However, instead of being able to mark the new skill (or specialization) down under the "General Career Advances" section, Bob woul dneed to record it under the "Non-Career Advances".
Bob decides to purchase an Action card. He looks through the cards, and chooses "Mighty Blow". Bob can swing his rake with the best of them. Again, under the "General Career Advances", this time where it says "Action Card", Bob enters the name of the Action card he chose: "Mighty Blow".
Bob plays a third session and gains a third XP. Bob has realized that Bob isn't very good in social situations. Bob wants to impress the ladies, so he decides to take another Action card, "Flirtation". Since the Gardener career has "2" under advances for actions, this new action card is still considered an "in-career" advance. Looking at the "General Career Advances" section, the specific "Action Card" line has already been used. So, Bob would write down "Flirtation" under one of the "Open Career Advance" lines.
Every character is required to fill in the four specific lines in the General Career Advances section. So, Bob now has 10XP and has taken the following advances:
2x Action cards
1x Reckless stance
Bob has saved up the last 3XP, and now has 4XP, in order to raise his Strength from 3 to 4. The four empty "Open Career Advance" lines are all filled in with "+Strength". He has spent all 10XP.
At 10XP gained(not spent) Bob became Rank2.
[Edit: As a note, Yes, his 10th XP point *could* be spent to Train in Resilience a second time, as Bob is now rank 2. However, as mentioned above, the Gardener career only has 1 in-career advance for skills, so Training Resilience a second time would not be an in-career purchase]
He is still in the Gardener Career, however. Bob has fulfilled all the requirements for compeleting the career:
1) He has purchased 1x action card, 1x talent, 1x skill, and 1x wound.
2) He has purchased a total of 10 in-career advances.
[ As an alternate note/mention, suppose that in there Bob had chosen to purchase training in Weapon Skill so he can wield his Rake better. Weapon Skill is not a career advance, so it will cost Bob 2XP. This means that Bob would not be able to complete the Gardener career until, at a minimum, Bob gains 12 XP total.]
Keep in mind that Bob is still currently in the Gardener career. Now, Bob is a Reiklander/human. As such, his career transitions are cheaper. If he wanted to transition to another career that was similar enough, he might be able to do so right now if it had an XP cost of 0. However, he would not get the dedication bonus.
Bob decides he wants the dedication bonus. So, he plays an 11th session as a Gardener (despite the career being "completed") and gains another +1 XP at the end of it. Yay! Bob now pays the 1XP for the dedication bonus. First, he gets to keep the Gardener career ability permanently. Second, Bob trained Resilience during the career, so Bob gets a free specialization in Resilience. Bob chooses Resist Disease, based on his long association with fertilizer/manure.
So, I know this was kind of long, and somewhat hypothetical. Does this help at all, though?