Help – how do I implement strategies requiring executing multiple trades immediately?

I’ve been running analysis on variations of the iron condor / iron butterfly strategies and am able to come up with relatively low risk strategies that I’d like to execute. The strategies often involves 3 or 4 trades (i.e. write and buy options), at different strikes.

The problem is, by the time I’ve executed the trade my opportunity for profit has eroded as the prices have changed (note: I’m testing on a demo account presently).
Additionally, if one of the trades do not go through, it can leave me exposed.

How are others executing multi-leg trades?

I’m currently using SaxoBank, and my preference is to trade XJO on the ASX. I’m open to trading other markets if XJO / the ASX isn’t an option to achieve the above, but would prefer to trade a cash-settled asset.

Any suggestions would be much appreciated!