Let's face it, not everyone can afford $300 for a custom-made athame, or a one-of-a-kind silk robe. But having to work within a budget doesn't have to cause problems, and it certainly doesn't mean your a 'bad Pagan'.
Being spiritual itself doesn't cost anything, so it's likely that most financial constraints will come into play when you're getting supplies or tools for your altar. So that's where I'm going to focus my suggestions.
Nothing wrong with homemade - You'd be surprised how many tools or supplies you can craft all by yourself. A little bit of elbow-grease and some creativity can go a long way. Besides, any tool that you've put your own energy into will be better than store-bought.
Learn where to shop - Find where the local thrift shops and dollar stores are. Sacred tools don't necessarily need to come from a Pagan shop. With a watchful eye, you can find lovely candle-holders, incense burners, chalices and even statuary in unexpected places. Books can sometimes be purchased second-hand, or found at the library.
Do without - The ultimate cost-savings, don't buy at all. Tools can help you focus and can add energy to your work, but they are not really necessary. If you really find your ends don't meet, then adapt your rituals to work without certain tools altogether.
Learn to adapt - Don't get in a rut, thinking that your tools have to be certain things. What matters is how you view them. Here are a few examples:
Book of Shadows - Your BoS doesn't need to be a leather-bound tome with brass clasps and parchment paper. Make do with any blank notebook (hard covered sketchbooks are quite nice). If you want to be able to move pages around, stick with a plain 3-ring binder.
Athame - So what if a traditional athame is double-edged with a black handle? Any knife will do, or you could even use an attractive letter opener as a sacred blade.
Cauldron - It can be tough to find a typical three-legged, cast-iron cauldron, and you'll likely pay top-dollar at a Pagan shop to get one. Any heavy, fire-proof dish or bowl can be used as a cauldron.
The bottom line: it's the thought that counts. What's in your heart is more important than the price tag. Don't feel badly that you can't afford certain items. That guilt will get in your way much more than anything else.