First off, welcome!
As you probably already guessed, there's no single absolute answer to "whether I invest my time a lot further". My view is that the single biggest factor playing into a decision whether to take the leap into Quantopian (or algorithmic trading in general) is if you enjoy it. Do you enjoy coding, creating algorithms, analyzing problems, researching and developing ideas, going where no man has has gone before (and so on)? If software and finance aren't something you already do and enjoy doing and have an aptitude for, then you may find the learning curve vs the rewards is too high and will probably loose interest fairly quickly. I'd speculate (but would really like to know if Q would share) that the 'turnover' on Quantopian is very high. Of the 100,000 purported users only 1000 or so stick to it for more than 6 months. Of those, maybe half participate in the contests and/or live trade their algorithms. I'd venture the main driver for those individuals is a Sheldon-esque passion for the process (though maybe I'm just speaking for myself).
The second biggest factor that plays into "whether I invest my time a lot further" however, is one's capital base. How much money do you have available to invest? If you have $5000 and really enjoy it, then by all means, jump in! You probably won't get rich but you'll have fun and maybe make a bit of profit along the way. If you DON'T really enjoy it, then go do something you love. One won't succeed where there isn't passion.
However, if we're talking $500,000+ and one is expecting to live off their investments at some point, then the calculus changes a bit. It's my opinion that there are only three reasonable approaches to investing. 1 passive investing (buy a stock and a bond ETF and rebalance quarterly or something similarly passive), 2 actively managed investing (hire a money manager to more actively manage your funds but just make sure they are netting you more than the market with less volatility and their name isn't 'Bernie'), or 3 algorithmic trading. If you have the capital and are expecting to earn a large portion of your income from that capital, then it may make sense to explore option number 3 if one is at all inclined towards programming and finances.
So, with that in mind, here's my answers...
The most successful algo, what type of margin would they expect 10% per annum? Obviously this depends on whether we are in the bull or bear market how would they then to perform vs the market?
I read your question as "what is a reasonable expectation for annual return? Is 10% reasonable?" and "how do algorithms perform vs the 'market'?". What's missing in the question is volatility and drawdown and how long that drawdown lasts. Without ones expectations for volatility, then returns are meaningless. If one is willing to put up with a 50% drawdown for a year (ie start with $100,000 and see it drop down to $50,000 and not be back to breakeven for a year) then you could get a 50% average annual return. (Simply invest in XIV). However, most mortals don't have the stomach for that and would have thrown in the towel after a couple months of losses. So, I'll posit a more palatable drawdown of 12%. That's less than the volatility and drawdown of the S&P500 over the past 5 years. I'd say one should expect to do about 50% better than the market (ie SPY). Over the past 5-7 years the market has averaged about 12%. A reasonable algorithm should return about 18%. Attached is a VERY simple algorithm which hits these targets in a bull market like we've had lately. Containing the downside risk when the market isn't doing so well is the challenge however. Here is a link to a contest winning algorithm https://www.quantopian.com/posts/contest-8-winner-robert-shanks. Look at the notebook in the post which shows an annual average return of 16% and volatility of 11%. That might be a good benchmark.
How long does it take to get something "ready" that is profitable. What do you think the minimum would be?
My advice is to start trading as soon as possible with a simple algorithm (maybe similar to the one attached) to get the 'feel' of trading. Then incrementally make improvements. First focus on reducing the volatility, max drawdown, and drawdown time. Then focus on increasing returns. Look through these forums for ideas and help. You will find that returns are often the easy part (just add a little XIV or leverage to any strategy :) ). If you have a bit of aptitude and spend a few hours a couple times a week, my guess is that you'll feel comfortable with the tools and have made some solid headway in 6 months.
ps: I can post a 'Robinhood friendly' version of this algorithm which you could use out of the box. No guarantees but I have traded with it. Let me know.