Question about margin and pyramiding

Hi Pat, I would like to ask 2 questions:

1. Usage of margin: I haven't used this too much in the past. As a beginner how much % of margin would you recommend to buy stocks on ? In case you use full margin, if you have $10.000, for example, combined it would result in $20.0000. If you originally planned to buy 5 stocks on 10K (i.e. 2K per stock). Do you now use 5 stocks on 20K (i.e. 4K per stock) or buy 10 stocks on 20K (i.e. 2K per stock) ?
2. Pyramiding when working during daytime: How to do this ? Do I place 3 buy stop orders with contingent sell stops in advance ? Example: when 1. buy point (BP) is at 40$ and contingent sell stop is at 38.8$ (3% under 1st BP), 50 shares. Then 2. buy point is at 40.8$ (2% above 1st BP) and contingent sell stop is at 39.58$ (3% under 2nd BP), 30 shares. Last and 3rd buy point is at 41.60$ (4% above 1st BP) with sell stop at 40.35$, 20 shares. Is this right ? The 3% contingent sell stops are based individually per buy point (i.e. there is no common sell stop for all 3 buy points) ?

As always I'm grateful for your feedback. Best Regards, TJ