I would start with some basic scenery like trees, assuming your track is already good to go.

yes I’m using his old set up its like 8 ft by 4 ft

Welcome to the world of Model Railroading!! In my experiences, Hobby Lobby is not a cheap place to purchase model railroad supplies. That being said, they do have a nice supply of scenery Items and paints. You mention ‘his old set-up’, what exactly does that entail? Is it just track, no scenery? Old scenery that need to be refreshed or redone from scratch? Do you just want to add to what is already there? A 4×8 is nice size for N-Scale! Can you post some photos to better assist you?

First off determine the the size if your layout, then select your scale, you want to use. remember the larger the scale the more space it will need. Then decide what you want to model, urban, rural, industrial. put together a list of what you will need to make your vision complete. find a local club and pick their brains, they can help you fine tune your ideas and maybe help you put it together, They can also help you with purchasing what you need. There is also an organization called the NMRA which has numerous resources to assist you as well. Planning it all out in advance can make it easier, when it comes to building your layout. Good Luck

Welcome to model railroading! Before you purchase anything, maybe draw out on scap paper what you want. If you have a computer, Anyrail is a free (up to 50 pieces) program to help you plan things out. When i have an idea i usually go paper first, then use Anyrail to see if it works. If not, on Anyrail i make the adjustments. Hope this helps!

I always suggest to people join a club or group to get to know others in your area that are also into model trains. You can share tips and tricks, also look like for model train shows. Start small and stay within your budget. Enjoy the hobby.