To what extent is a person's success in the field determined by the first 1-2 jobs they have?

Not nearly as much as you may think. An alum recently came to my MBA school to speak. He was making I kid you not $7-10K post MBA in Eastern Europe doing interesting strategic / M&A work for small scale companies, he went that route as the economy in the early 1990s wasn't great. Eventually found his way back to the States to work in a M&A role at a mid sized company. Mid sized company proceeds to get purchased by a bigger company that eventually became a Fortune 50.

Went from M&A (50+ acquisitions under his belt) to administrative / HR work to eventually (now) running a $50B business unit. Not sure what his comp is but based on what I think the corporate structure is like, he reports to someone right below the CEO and both of those above him make at least $10M.

Look at all the people who didn’t start off as analysts in ib, in both finance and non-finance fields. A good place to start but not a requisite to do well long term 

It depends on the person, clearly if your first 2 jobs are in the waste management division then Blackstone may be a bit harder to get down the round, but there may always be unexpected opportunities and luck in one's career that can completely change one's path.

But the importance of the first jobs for me is that it builds a type of compound effect in terms of knowledge. If you stay in the same field you build knowledge on top of knowledge and you can get a more advanced understanding of the field. If you come from a remote field then there is also validity in that, in the sense that you can make connection with your current field and the past field (for example doctors that get investment roles are able to analyze trends and companies also through the medicine industry lens, lawyers that get finance roles also can pass through their legal lens some transactions/risks, etc.).

It could play a positive role if you start out at a strong group and make the most of your experiences in these places, but a lot of people seem to build better momentum later on in their lives. People in their early to mid 20s often go through a time of uncertainty in what they want to do for work or what avenues to explore, so some may just take longer to figure it all out than others. Keep an open mind, seek out opportunities that benefit you and constantly try to learn and improve yourself each day

I know someone who started out doing basic operations work for an hotel and eventually worked his way up to running his own REPE shop buying hotels. Never went to college. It happens. 

To a very large extent

what is "somewhere good" to you?  99.99999% of successful business owners did not attempt to embark on some pre defined finance path.

I think the misconception on this forum about people following IB/PE/HF path being set for life is absolutely hilarious, how many seats do people think exist in banks,pe shops, hfs vs the wave of banking interns that come through each year? the people that perpetuate this myth must be a) very junior/coming out of school or b) incapable of simple calculations

but to answer the question, if you think IB/PE is "somewhere good" post a sluggish start, yes I've seen it a million times. but my point is that IB/PE being the land of milk and honey is inaccurate. 

It could matter a little but if you have a fixed mindset or get comfortable in a place that you didn’t necessarily want to work then it may have a larger impact 

Some people find success later into their lives. Don’t spend time comparing to people who went to work at Apollo, BX, CVP, EVR etc those are great paths but not the only ones

It could play a factor, but a lot just depends on the individual and it’s just different depending on how you go about your journey. You can choose to recruit for better roles or stay in roles you’re unhappy with. To each their own 

The more narrow your goal is, the more they matter. If you feel you HAVE to walk the path of H/W -> MF PE, then yeah, it matters a lot, but if your goals are more broad, not as much

I think it’s interesting when IB candidates and analysts think doing IB out of undergrad is the only path to success but that’s not the case with careers and people can start in other areas and can most likely do well if they put in as much effort as anyone working in ib who worked up to MD

Probably if you would rate the first job on some scale from 1->10 and look at the R squared for net worth 20 years later my guess is it would be >50% 

Sadly it has an outsized impact. It's not dissimilar to when you graduated, those who graduated into the financial crisis still make far less than those who graduated 3yrs earlier or 3yrs later at the same point in their lives. First job matter a lot but can be overcome with a 2nd job that's stellar. After that if you've got 2 mediocre jobs under your belt future folks will see a pattern of mediocrity and you'll be less likely to get the best shots on goal moving forward. There are exceptions, but we're talking about 80% of folks, not the 20% of those who break this mold 

I guess it depends?  If you want to work at that company for forever, then of course it matters.   And doing a good job and building a reputation is important.

But in the sense of "what are those first few jobs"?  I don't think it matters much, within reason.  I mean, if you're flipping burgers for your first two jobs, I think it's a long road to being a managing director at Goldman Sachs.  But plenty of people lateral into other industries.