it is not at all economic to buy €50/100 shares per month.
you will face a min charge on buying/selling of €20 per transaction, with 1% stamp duty if an Irish share and 1/2% is a UK share.
You will also have a yearly fee if in a nominee or sponsored crest account. if you wish to be a certificated shareholder, then you will not be able to sell until the share cert is in possession of the selling broker, thus incuring postage costs.
If you bought €500 of a share, using my figures and assuming it was an Irish share, the costs would be €25. the selling cost at €1000 would be €20. If you had yearly fee, you would have to factor that in as well.
You would not have any capital gains tax, if the only gain you made in the year was €500 as you are withing the tax free amount.
Chances of making 100% in a year is poor!