Starting a small amount on trading is better especially to those first time on trading because their is possible that your capital on trading got lose. Try to study the coin before you buy see if that coin have a good dev and have a good project before you buy.
Trading may be started from small amount so as to avoid risk initially. Market should be monitored properly before buying bitcoins. It also depends on the capital of trader that how much he wants to invest initially. Help may be taken from expert traders as how they manage their business. YouTube may also be checked for proper guidance.