You keep the MSF Avatar until you reach 20 trades, but if your Trader Rating falls below 5.0, then you still have it until you get up to 5.0. You have very few trades right now, so it wont take long to get that rating up.
Just make sure that the cards you are sending out are
1.) In good condition
2.) You mail them out promtly or on a agreed upon date with the other trader
3.) Keep the communication going and reply back to the other traders promptly if possible.
When in doubt about any trade you have in works, ask the other trader you are working a deal with or ask a MOD for help.