Need a little help with this on live dealer

[AcidRains]

Hi all, new member and my first post here,
i got this method played for few days , and get a few profit with it, but still get not enough confidence \
so does anyone around can help me do a little testing spins, maybe 500 spins or more and see how does it go in long run?

the way i play:
whenever one dozen hit twice, bet two dozens against it, using 3-3,6-6,18-18,54-54 four step progressions,

for example:

3
7 《＝＝now bet 2nd and 3rd dozens
18  win3 （if lose keep betting with above progression）

i'm seeking to know how further i can go before busted, and how safe is four step for this coz i've seen few times i ended up in 4th step ( or should i make it to 5th step progression to get more safe）
and also curious is this method better or worse than using code four ? maybe some one kind enough to make a comparison chart?

if my target is to win 5 bet per session and i only won at first bet with above mentioned progression, is it better if  i play 3 step progression 3-3,9-9,27-27 to win every bet instead of 4 steps but more risky?
just intend to make a little steady income and  sorry for any grammar error as english not my mother languange,
any suggestions and kind advice is very much appreciated and thanks all for reading