if you expect yourself to be competitive at max. level.... no its not f2p friendly...

If you are willing to take slow road, save up currency and limit your XP gain (freeze lvl) and you have have patience.. it is sort of f2p friendly.
By that I mean, you will always meet someone of your level stronger (unbeatable), because he pays...
All power gaining features are double edge swords... On one hand, you get power, on the other its another feature you fall behind at to paying players..

All I can advise you as a fellow f2p is:
- spend wisely (you are f2p, go for support ninjas / meta ninjas with some lifespan... we cannot affort to have all ninjas to make teams, we have to pick up ninjas to use them to their fullest)
- max up rebates (as much as you can)
- find a team you wanna go for (pretty much the 1st point), get a team ready to be competiitive... and get at least 1 competitive team (you can experiment later, but stay competitive)
- in most cases Power > ninjas... on the other hand I lost to 6p teams with JMinato team with less than 30k power (me 100k, them 70k... just because I went to power up whole team while they powered 6p and I lost round 10) .... getting to another point....
- stack up your pos1, unfortunatelly even is your whole team is at 100k power (fairly distributed power 26-23k power between all 4 ninjas) you will pretty much lose to a team with stacked pos1 (100k power team - 40k power pos1 and 20k others)...

try to stay as low lvl as you can... once you get into beast´s territory, you can´t get out... and a lvl 73 with 150k power is ready to hunt down any weak guy xD

good luck