I completely agree, the unstable returns at low levels are horrible for player retention.
That said, there are ways to build up a bankroll without depositing. It can take a while though. Probably easiest is to use one of those survey / crowd source work sites that have game card / PED rewards. But I assume you want to earn it all in game, so:
1) Sweating -of course, everyone knows this, right? Sweat yourself up around 20 PED, do it on puny mobs if you like to sweat alone or hit up ambulimax if you prefer a group.
2) This step is a bit more fun... sort of, lol. Got your 20 PED? Great! I'm not sure what gear you have already but if you don't have an opalo, grab one and put the rest of that 20 PED in ammo. Swunting will be the name of the game. Find yourself a swunting team, you get people to talk to and you kill mobs after they're dry so a bit less boring that just sweating. The sweat helps cover your ammo costs on killing the mob making it MUCH easier to profit on the loot.
You can even profit slightly swunting puny mobs solo but then you lose the social aspect and the chance at nicer loots. Also don't use the opalo on puny mobs, too much overkill.
3) Trading - It's not rocket science, but it can be boring. It can also bring you quite a bit of PED if done right. When you've built up enough PED swunting you can get into this to speed up your growth, or skip it, up to you. A good place to start might be making your own mind essesnce to get the most from your sweat. Probably they cheapest item to start trading with is animal muscle oil, low TT and low MU mean a low barrier to entry.
4) Mining - Once you have a good bankroll going from swunting and/or trading you can begin to mine effectively. Do your research, don't just run around dropping probes randomly. If you assume 90% average returns then than means you need to find ores that average over 112% MU. There are ore maps all over the internet, I also suggest using Little Big Mining Log's app.
Well, there it is. The road from zero to a 1k PED bankroll without depositing. It's long, it's boring, but it can be done if you really want to.
Short road? Put in a small deposit every month. Even $5, if you use that money for cheap activities, like swunting, your bankroll will grow each month.