Congrats on your new camera.

There are many alternatives when it comes to lenses and you would be wise not to rush to quickly in making your choices as mistakes can be expensive.

The cheapest way for you to cover the type of shots you want to take is to buy some extension tubes to go with the kit lens you have. Kenko do a set of 3 for less than $200 by using the 25mm & 30mm tubes together with your kit lens you will have 1:1 macro photography.  

Their main disadvantage is they do require good light to work well so conditions have to be bright or use a tripod.  They lack some of the convenience of just putting on a macro lens.   

Advantages are cost, making use of the lens you have, and versatility you can use them in any combination on any lens so they will always be useful even if in the future you buy a dedicated macro lens. 

 

My second alternative is to buy a used macro lens. Quite often these appear because people upgrade to a more expensive model. Good examples can be found of the Tamron 90mm. Sigma 105mm and Canon 100mm macro lenses. They are all good quality lenses - buy from somewhere that offers a guarantee or that you trust,  if you are not used to looking at lenses.

 

My third alternative is to buy the Canon EF-s 60mm macro that can be bought for less than $400 and is a high quality dedicated macro lens that will work very well with your  Canon Rebel.

 

For landscapes the kit lens you have is quite adequate until such a time as you can afford to buy a dedicated wide angle landscape lens. There are many other purchases you will need to make before upgrading this.

 

HTH - Richard.

And every one said, 'If we only live,
We too will go to sea in a Sieve,---
To the hills of the Chankly Bore!'
Far and few, far and few, Are the lands where the Jumblies live;
Their heads are green, and their hands are blue, And they went to sea in a Sieve.

Edward Lear
http://www.nonsenselit.org/Lear/ns/jumblies.html