The best argument for a small opening deposit has nothing to do with markets. You're testing a process — signup, verification, funding, a first position and, most importantly, a withdrawal — and that test should cost as little as possible.
Run the full loop with the minimum deposit. Put money in, wait, take some back out, and watch how long it takes and whether it returns to the method you used. A platform that handles a small withdrawal cleanly is one worth trusting with more.
Only after that round trip does it make sense to think about size, and even then in steps rather than one big move. A bigger deposit doesn't make a strategy work better — it just makes the same outcome larger in both directions.
Why the first deposit matters most
The first deposit sets the habit. An amount chosen because it's comfortable tends to lead to calm decisions; an amount chosen because it felt like the ceiling tends to lead to decisions made under pressure.
A workable starting point
Money you wouldn't need back within a year, in an amount whose loss would be annoying rather than damaging. That's a personal figure and nobody else can set it for you.
Adding to it later
Topping up a balance you already understand beats starting large and learning the hard way afterwards.
Questions worth asking before you send anything
How do I withdraw, and to where? What gets deducted, and by whom? Who do I contact if something looks off? A platform that answers all three clearly, in writing, is behaving the way it should.
Investing involves risk, including the possible loss of some or all of the capital you invest. The value of investments can go down as well as up, and you may get back less than you originally put in. Never invest money you can't afford to lose.