I'm still waiting for additional money but i wonder if i can do transaction now with change i've got, and then (if it dosen't get confirmed) do a rbf with that new transactions when satoshis arrives.
Yes, this is possible.
You can make a CPFP transaction now, and then later use RBF to bump the fee of the CPFP transaction if it does not confirm. The only limitation here is that your RBF transaction can only include an unconfirmed output if the transaction it is replacing also contained that same unconfirmed output. What this means is that any additional funds you want to add in to the RBF transaction (such as those you are waiting on arriving) must have confirmed before you can include them.
Other option is to do cpfp and leave 1 satoshi from that change, and do another cpfp when i get additional resources.
The minimum amount you can leave as change 546 satoshi in a legacy address or 294 satoshi in a segwit address.
But never done rbf, its just changing the fee or is there any catch to it? Does it change weight of the tx or am i thinking right to try confirm with light tx and then add via rbf if it doesn't confirm?
The weight of the transaction would change if your replacement transaction included more inputs than the one you are replacing, such as if you were including an extra input of the coins you are waiting to receive.
Having said all that, I don't think there is much point. We know that at most you will be able to boost the fee to around 23 sats/vbyte, which will still put you around 8 MB from the tip. Either wait until 23 sats/vbyte may get you confirmed, or wait until you have more funds available to bump the fee higher.