You will find difficulty buying constance for your first 5* with your current resource.
I suggest you maxed all those 4* that you have and uptrade several of them into your first 5*.
Regular 5* usually cost around 2-3 m4* and the LE one can cost up to 5 m4* (some even more, so avoid them atm).
It will take time of course, but by doing this, you can save your precious TE for other purpose.
If you really desperate to have your first 5*, then you can find many ppl sell the regular 5* for around 10TE.
Hope that helps and good luck finding your first 5*..