Paris airport to Montmartre
 

I'll be travelling from Barcelona to Paris on 1 Jan 2016. From what I checked, the best way is to take a plane. But I'm not sure which airport to arrive at in Paris would be better for me. I'm also planning to stay in the Montmartre area since I'll be taking a train to London after 4 days. I need advice on:

1. Which airport to arrive at would be most convenient/safer for me. I'm a 20 year old Singaporean girl travelling solo so I have a luggage (+/- 25kg) to pull too
2. I'm definitely staying at the foot of Montmartre since I have a luggage so any hotels/apartments to recommend? I'm thinking less than 70 euros a night?

Take a taxi.
If you have so much luggage, don't bother with RER or whatever.

CDG might be a bit closer than Orly.
CDG is east of Paris, Orly is closer to center but south.

Less than 70 € in Montmartre is a challenge - but try these :
Ramey 24 rue Ramey 18e - I paid 70 €. Entrance looks bizarre but I had a great stay.

Victoire 18e (forgot the address) - more towards Barbes, so people like it a lot less (too many allochtone people for some) but good hotel - further from Montmartre.

Villa Montmartre Clignancourt, 44 18e : more like a small appt than a hotel room. About 100 e, so above ytour budget.

Try to negociate or at least look at booking.com, these prices I mention are not the standard prices (but who pays the standard price ?).

Enjoy Paris.

For Montmartre just take RER-B train to Gare du Nord, and choose a hotel that is within a few blocks walk. Vueling.com/fr has a flight at 10am and another around noon, arriving CDG which is a bit easier than Orly. Price is around 100euros, but note that some of the budget airlines only accept carry-on bags of 20kg now. You can pay to take a heavier bag, but do this when you purchase the ticket because if you wait til they catch it at the gate, you'll pay double or triple.

It's easy to get from Gare du Nord to many other neighborhoods with just one hop onto the metro, so don't limit yourself to Montmartre if you'd rather stay somewhere else. Maison du Pre is in your price range near Montmarte and an easy walk from the station....you can find it on booking.com with free cancellation in case you change your plans.

Gare du nord to Montmartre is quite a walk.

But good idea - maybe you go to GDN on RER then a small hop from there to Montmartre by taxi.
10 € from CDG to GDN, the 10-15 for taxi, instead of about 50 € from CDG to Montmartre as I recommended.